Co-reporter:Ruirui Liu, Xiao Zhou, Jiwei Zhai, Jun Song, Pengzhi Wu, Tianshu Lai, Sannian Song, and Zhitang Song
ACS Applied Materials & Interfaces August 16, 2017 Volume 9(Issue 32) pp:27004-27004
Publication Date(Web):July 24, 2017
DOI:10.1021/acsami.7b06533
A multilayer thin film, comprising two different phase change material (PCM) components alternatively deposited, provides an effective means to tune and leverage good properties of its components, promising a new route toward high-performance PCMs. The present study systematically investigated the SnSb4–SbSe multilayer thin film as a potential PCM, combining experiments and first-principles calculations, and demonstrated that these multilayer thin films exhibit good electrical resistivity, robust thermal stability, and superior phase change speed. In particular, the potential operating temperature for 10 years is shown to be 122.0 °C and the phase change speed reaches 5 ns in the device test. The good thermal stability of the multilayer thin film is shown to come from the formation of the Sb2Se3 phase, whereas the fast phase change speed can be attributed to the formation of vacancies and a SbSe metastable phase. It is also demonstrated that the SbSe metastable phase contributes to further enhancing the electrical resistivity of the crystalline state and the thermal stability of the amorphous state, being vital to determining the properties of the multilayer SnSb4–SbSe thin film.Keywords: electrical resistivity; fast phase change speed; metastable phase; phase change material; thermal stability;
Co-reporter:Shaohui Liu, Jiao Wang, Bo Shen, Jiwei Zhai
Ceramics International 2017 Volume 43(Issue 1) pp:585-589
Publication Date(Web):January 2017
DOI:10.1016/j.ceramint.2016.09.198
Abstract
Nanocomposite based on poly(vinylidene fluoride) (PVDF) polymer filled with surface functionalized core-shell structure BaTiO3@Al2O3 nanofibers (BT@Al2O3 NF) were prepared via the solution casting method. Experimental results clearly demonstrate that the nanocomposites with BT@Al2O3 NF exhibit enhanced discharged energy density under high electric field compared to those of BT NF. The maximum discharged energy density in the nanocomposite with 2.5 vol% BT@Al2O3 NF is 7.1 J/cm3 at 3800 kV/cm with an efficiency of above 65.1%. According to the results of complex impedance analysis, coating Al2O3 layers on the surface of BT NF reduces the Maxwell–Wagner–Sillars interfacial polarization, which might be the reason of the improvement of the discharged energy density and discharged efficiency. This work may provide an effective solution to enhance discharged energy density in polymer-based nanocomposites.
Co-reporter:Shaohui Liu, Jiao Wang, Jingyi Wang, Bo Shen, Jiwei Zhai, Chenguang Guo, Jingqi Zhou
Materials Letters 2017 Volume 189() pp:176-179
Publication Date(Web):15 February 2017
DOI:10.1016/j.matlet.2016.12.008
•Discharged energy density of BT@SiO2 NF/PVDF nanocomposite was investigated.•The properties enhancement mechanism of nanocomposite was proposed.•The efficiency of the nanocomposite films is 62.7% at 3500 kV/cm.Nanocomposite based on poly(vinylidene fluoride) (PVDF) polymer filled with surface functionalized core-shell structure BaTiO3@SiO2 nanofibers (BT@SiO2 NF) were prepared via the solution casting method. The effect of BT@SiO2 NF filler introduction on the discharged energy density performance of the nanocomposite were investigated. The results indicated that the discharged energy density of nanocomposites is enhanced and the maximum discharged energy density in the nanocomposite with 2.5 vol% BT@SiO2 NF is 6.6 J/cm3 at 3500 kV/cm with an efficiency of above 62.7%. The reason of the enhancement of the discharged energy density performance is that coating SiO2 layers on the surface of BT NF reduces the Maxwell–Wagner–Sillars interfacial polarization. This work may provide a novel route to enhance discharged energy density performance using core-shell nanofibers in polymer-based nanocomposites.
Co-reporter:Zhongbin PanLingmin Yao, Jiwei Zhai, Dezhou Fu, Bo Shen, Haitao Wang
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 4) pp:
Publication Date(Web):January 9, 2017
DOI:10.1021/acsami.6b13663
Flexible electrostatic capacitors are potentially applicable in modern electrical and electric power systems. In this study, flexible nanocomposites containing newly structured one-dimensional (1D) BaTiO3@Al2O3 nanofibers (BT@AO NFs) and the ferroelectric polymer poly(vinylidene fluoride) (PVDF) matrix were prepared and systematically studied. The 1D BT@AO NFs, where BaTiO3 nanoparticles (BT NPs) were embedded and homogeneously dispersed into the AO nanofibers, were successfully synthesized via an improved electrospinning technique. The additional AO layer, which has moderating dielectric constant, was introduced between BT NPs and PVDF matrixes. To improve the compatibility and distributional homogeneity of the nanofiller/matrix, dopamine was coated onto the nanofiller. The results show that the energy density due to high dielectric polarization is about 10.58 J cm–3 at 420 MV m–1 and the fast charge–discharge time is 0.126 μs of 3.6 vol % BT@AO-DA NFs/PVDF nanocomposite. A finite element simulation of the electric-field and electric current density distribution revealed that the novel-structured 1D BT@AO-DA NFs significantly improved the dielectric performance of the nanocomposites. The large extractable energy density and high dielectric breakdown strength suggest the potential applications of the BT@AO-DA NFs/PVDF nanocomposite films in electrostatic capacitors and embedded devices.Keywords: BaTiO3 nanoparticles; capacitors; dielectric properties; energy density; nanocomposites; one-dimensional;
Co-reporter:Baihui Liu;Xing Liu;Peng Li;Feng Li;Bo Shen
RSC Advances (2011-Present) 2017 vol. 7(Issue 66) pp:41788-41795
Publication Date(Web):2017/08/23
DOI:10.1039/C7RA07711D
In this study, 〈001〉-textured (1 − x)K0.48Na0.52Nb0.96Sb0.04O3-xBi0.50(K0.48Na0.52)0.50Zr0.50Hf0.50O3 [abbreviated as (1 − x)KNNS-xBKNZH, x = 0.01–0.04] lead-free ceramics were prepared by templated grain growth (TGG) method and sintered by a two-step process. Excellent longitudinal piezoelectric coefficient d33 (434 pC N−1) and piezoelectric strain coefficient (722.5 pm V−1) are achieved in the textured 0.97KNNS-0.03BKNZH ceramics. The excellent piezoelectric properties can be ascribed to both the coexisting R–O–T multiphases and the 〈001〉 crystal orientation. In addition, a high electromechanical coupling coefficient kp (∼73.6%) is attained in textured ceramics with x = 0.02. The values of d33 and kp also display high thermal stability (with rate of change < ±10%) over 25–120 °C in textured ceramics with x = 0.03 and 0.04. Excellent comprehensive properties suggest that 〈001〉-textured (1 − x)KNNS-xBKNZH ceramics are promising lead-free candidates for actuator and transducer applications.
Co-reporter:Peng Li, Jiwei Zhai, Bo Shen, Wei Li, ... Kunyu Zhao
Journal of the European Ceramic Society 2017 Volume 37, Issue 10(Volume 37, Issue 10) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.jeurceramsoc.2017.03.024
Low-lead-content (1-x)(Bi0.5Na0.5)TiO3-xPbTiO3 (x = 0, 0.05, 0.10, 0.15, 0.25) (hereafter abbreviated as BNT-xPT) thin films were prepared by a sol-gel method, and their crystal structure, dielectric properties, recoverable energy-storage density and piezoelectric response were investigated as a function of PT concentration. Combining the XRD patterns and Raman spectroscopy indicate the phase structures go through rhombohedral (R) – rhombohedral + tetragonal (R + T) – tetragonal (T) evolution with increasing of PT content. A high recoverable energy storage density of 13.02 ± 0.39 J/cm3 was achieved in the BNT-0.10PT thin films due to the high field endurance and significantly enhanced polarizability. Moreover, a superior piezoelectric response (d33* = 120 ± 5 pm/V) was also obtained in the 10% PT-modified BNT films, which can be attributed to easy polarization rotation due to low polarization anisotropy on the R-T phase boundary. These properties indicate that BNT-0.10PT films might be promising multifunctional materials for piezoelectric micro-actuator and energy storage embedded capacitor applications.
Co-reporter:Weihua Wu;Shiyu Chen
Journal of Materials Science 2017 Volume 52( Issue 19) pp:11598-11607
Publication Date(Web):05 July 2017
DOI:10.1007/s10853-017-1340-y
The phase change behaviors of titanium antimony thin films were examined as a function of Ti concentration by in situ electrical measurement. With the increment in titanium content, the crystallization temperature enhanced, while the electrical conductivity reduced. The sharp decline in carrier density is responsible for the drop of the electrical conductivity before and after crystallization. The amorphous and polycrystalline state was confirmed by means of selected area electron diffraction. The shift of Raman modes associated with Sb upon the phase transition was observed. The surface morphology and density fluctuation were obtained from atomic force microscopy and X-ray reflectivity. The interfacial adhesion strength between the titanium antimony thin films and silicon dioxide was implemented by Nano Indenter®. Based on Arrhenius plot and Johnson–Mehl–Avrami model, the crystallization kinetics including the crystallization activation energy, the crystallization mechanism and the Avrami coefficient were investigated as well. The obtained values of Avrami indexes illustrate one-dimensional growth-dominated mechanism of titanium antimony thin films.
Co-reporter:Yang Zhang;Baihui Liu;Bo Shen
Journal of Materials Science: Materials in Electronics 2017 Volume 28( Issue 15) pp:11114-11118
Publication Date(Web):12 April 2017
DOI:10.1007/s10854-017-6897-3
(1−x)(K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O3−xMZrO3 (M = Ca, Sr, Pb, Ba) ceramics with ABO3 structure were synthesized by conventional solid state reaction route. The effect of different kinds of dopant on orthorhombic–tetragonal (O–T) phase boundary and phase transition temperature were investigated, and the tolerance factor (t) of four kinds of zirconate dopants effect on piezoelectric properties was evaluated at O–T phase boundary. A quantitative relationship between O–T phase boundary and t was developed, the excellent piezoelectric properties was obtained when the t value at the O–T phase boundary in KNN-based lead free ceramics was around 0.9965–0.9990.
Co-reporter:Xing Liu, Jiwei Zhai, Bo Shen, Feng Li, ... Baihui Liu
Current Applied Physics 2017 Volume 17, Issue 5(Volume 17, Issue 5) pp:
Publication Date(Web):1 May 2017
DOI:10.1016/j.cap.2017.02.023
•The local structural transitions of NKBNT ceramics were confirmed by the temperature-dependent Raman spectra.•The dielectric local maxima and discontinuous changes on Raman spectra stem from the thermal evolution of R3c and P4bm PNRs.•The macroscopic changes of non-polar phase were investigated by the temperature-dependent electrical measurements.In this work, the temperature-induced structural evolution in 0.79(Na0.5Bi0.5)TiO3-0.2(K0.5Bi0.5)TiO3-0.01(K0.5Na0.5)NbO3 (NKBNT) lead-free ceramics was investigated by Raman microscopic spectroscopy combined with electrical macroscopic measurements. The NKBNT ceramics possess the local structure with the coexisted rhombohedral R3c and tetragonal P4bm polar-nano-regions (PNRs). The R3c and P4bm PNRs coexist in a wide temperature range, then the local structure transforms to the P4bm PNRs around the temperature of dielectric maximum (Tm) evidenced by the doublet splitting of Ti-O modes (peak B) and oxygen octahedral vibrational modes (peak C). The discontinuous changes of wavenumber and line-width of peak B2 and peak C3 as well as the dielectric local maxima around the rhombohedral-tetragonal phase transition temperature (TRT) are considered to result from the thermal evolution of R3c and P4bm PNRs. The macroscopic changes of non-polar phase with electric field and temperature were investigated by the temperature-dependent polarization-electric field (P-E) loops, current-electric field (I-E) loops and bipolar strain (S-E) curves. The electric-field level necessary to form the long-range ferroelectric order from non-polar phase associated with the stability of the induced ferroelectric phase depends strongly on the temperature.
Co-reporter:Feng Li, Ke Yang, Xing Liu, Jian Zou, ... Huarong Zeng
Scripta Materialia 2017 Volume 141(Volume 141) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.scriptamat.2017.07.010
The temperature dependence of energy storage and charge–discharge properties of a lead–free 0.62Bi0.5Na0.5TiO3–0.06BaTiO3–0.32(Sr0.7Bi0.2□0.1)TiO3 ergodic relaxor ferroelectric ceramic were investigated. The energy storage density was maintained ≥ 0.5 J/cm3 up to 140 °C with a high efficiency ≥ 90%. The stored energy was released in sub–microsecond durations and charge–discharge performances were enhanced as temperature increased to 160 °C. This ceramic possessed an enhanced power density 18.2 MW/cm3 and large current density 606 A/cm2. All results showed that this ergodic relaxor ferroelectric ceramics appeared very promising for pulse capacitor applications.Download high-res image (128KB)Download full-size image
Co-reporter:Zhongbin Pan, Baihui Liu, Jiwei Zhai, Lingmin Yao, Ke Yang, Bo Shen
Nano Energy 2017 Volume 40(Volume 40) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.nanoen.2017.09.004
•The NaNbO3 two-dimensional platelets as fillers incorporation into the polymer matrix was proposed first.•Excellent discharge energy density of 13.5 J cm−3, superior power density of 2.68 MW cm−3, and ultra-fast discharge speed of 0.127 μs were obtained.•Finite element simulations reveal the significant implications of trilayered architecture on the dielectric and energy storage performances of polymer composites.Polymer-based dielectric materials with high power density, high energy density, and broad operating temperature range are critical to the development of cost-efficient and lightweight capacitors for modern high-power electrical systems. Here, NaNbO3 (NN)/polymer composites, especially two-dimensional (2D) NN platelets, were used to create new composite films for energy storage applications for the first time. The trilayered architecture composites comprised of two outer layers of 2D NN platelets dispersed in a poly(vinylidene fluoride) (PVDF) matrix to provide high dielectric constant and a middle layer of pristine PVDF to offer high breakdown strength. The breakdown strength and energy density of the trilayered architecture composite films were improved significantly via tailoring the contents of the 2D NN platelets. The composite films with an optimized filler content illustrate a high discharge energy density of 13.5 J cm−3 at 400 MV m−1, far more than the best commercial biaxially- oriented polypropylenes. Moreover, the composite films show a superior power density of 2.68 MW cm−3 and ultra-fast discharge speed of 0.127 μs. Finite element simulation further revealed the breakdown strength and energy density of the composite films were much enhanced compared to the corresponding single layer composite films. Therefore, the new trilayered architecture composite films can be applied as an alternative promising high-performance electrostatic capacitor material.Download high-res image (282KB)Download full-size image
Co-reporter:Ke Yang, Jingran Liu, Bo Shen, Jiwei Zhai, Haitao Wang
Materials Science and Engineering: B 2017 Volume 223(Volume 223) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.mseb.2017.06.011
•Enhanced maximum energy storage density reached 12.14 J/cm3.•A quite rapid discharge speed with a discharge period of 25 ns.•Discharge efficiency approaches to 80% higher than the ceramic systems.Potassium barium niobate-based glass ceramics doped with different proportion of Gd2O3 were fabricated by conventional melts and controllable crystallization. The influence of Gd2O3 content was further investigated on the phase compositional change, energy storage performance and charge-discharge properties of the optimized glass ceramics (crystallization temperature 900 °C). The microstructure has been remarkably transformed through the addition of Gd2O3. On the basis of the results, the doping of 1.0% Gd2O3 achieved a remarkable improvement on the energy storage density that reached 12.14 J/cm3 with a dielectric breakdown strength (BDS) of 1818 kV/cm and dielectric constant of 83. The discharge efficiency of 80% and discharge time of 25 ns were obtained in the glass ceramics with 1.0% Gd2O3, which illustrated the excellent charge-discharge properties of Gd2O3-doped glass ceramics.
Co-reporter:Shuangxi Xue, Jiwei Zhai, Shi Xiao, Shaomei Xiu, Bo Shen
Materials Letters 2017 Volume 190(Volume 190) pp:
Publication Date(Web):1 March 2017
DOI:10.1016/j.matlet.2017.01.002
•Microwave heating technology.•Excellent energy storage properties.For pulsed power applications, the BaO–Na2O–Nb2O5–SiO2 glass-ceramic dielectrics were prepared by two routes including the traditional heating method and the novel microwave process. And the effects of the microwave process on the microstructure, the dielectric properties, and charge-discharge performance of the glass-ceramics were systematically investigated. The charge-discharge properties of the glass-ceramics were investigated using a high-speed capacitor charge-discharge circuit device. It was found that the microwave process could form a more uniform microstructure with small grain size, and significant enhancement on dielectric breakdown strength (1248 kV/cm) and discharge efficiency (92%) were achieved in BaO–Na2O–Nb2O5–SiO2 glass-ceramics crystallized by microwave process.
Co-reporter:Wangfeng Bai, Daqin Chen, Peng Zheng, Junhua Xi, ... Zhenguo Ji
Journal of the European Ceramic Society 2017 Volume 37, Issue 7(Volume 37, Issue 7) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.jeurceramsoc.2017.02.048
Recently developed Bi0.5Na0.5TiO3(BNT)-based piezoceramics face two urgent obstacles: high driving field required to trigger large strain and poor temperature stability. Highly oriented (1-x)(0.83Bi0.5Na0.5TiO3-0.17Bi0.5K0.5TiO3)-xNaNbO3 (BNT-BKT-xNN) piezoceramics were synthesized using NN templates to resolve both obstacles. Measurements of polarization and strain hysteresis loops as well as phase transition temperature revealed a phase evolution from ergodic relaxor to ferroelectric phases, generating a high strain of 0.43% and large Smax/Emax = 720pm/V for textured BNT-BKT-4NN ceramics. The field-dependent strain was largely depended on the degree of texturing. Most intriguingly, grain-oriented specimens provided excellent actuating performance characterized by both large Smax/Emax = 693 pm/V at a low driving field of 45 kV/cm and enhanced temperature stability with Smax/Emax = 537pm/V at 120 °C. This was basically ascribed to the facilitated switching between ergodic relaxor and ferroelectric phases owing to the grain-oriented structure. As a consequence, design of <00l> oriented microstructure opens the possibility to produce efficient BNT-based piezoceramics for transferral into real-world applications.
Co-reporter:Feng Li, Guorui Chen, Xing Liu, Jiwei Zhai, ... Haixue Yan
Journal of the European Ceramic Society 2017 Volume 37, Issue 15(Volume 37, Issue 15) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.jeurceramsoc.2017.06.033
The (0.94–x)Bi0.5Na0.5TiO3–0.06BaTiO3–x(Sr0.7Bi0.2□0.1)TiO3 (BNT–BT–xSBT, 0 ≤ x ≤ 0.24) solid solution ceramics were synthesized via a conventional solid–state reaction method and the correlation of phase structure, piezoelectric, ferroelectric properties and electrocaloric effect (ECE) was investigated in detail. The ECE in lead–free BNT–BT–xSBT ceramics was measured directly using a home–made adiabatic calorimeter with maximum adiabatic temperature change ΔT = 0.4 K with x = 0.08 under the electric field E = 6 kV/mm at room temperature. The position of maximum ECE was found in the vicinity of nonergodic and ergodic phase boundary, where the maximum change in entropy occurs as a result of the field–induced phase transformation between the ergodic and long–range ferroelectric phase. Besides, the mechanism for the shift of ECE peak is discussed in detail. Finally, the temperature dependence of ECE for BNT–BT–xSBT (x = 0, 0.04 and 0.08) was also investigated. This work may present a guideline for designing BNT–based ferroelectric relaxor ceramics for EC cooling technologies.
Co-reporter:Haitao Wang, Jinhua Liu, Jiwei Zhai, Zhongbin Pan, Bo Shen
Journal of the European Ceramic Society 2017 Volume 37, Issue 13(Volume 37, Issue 13) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.jeurceramsoc.2017.04.049
In this work, [xSrO, (1 − x)BaO]-K2O -Nb2O5-SiO2 (SBKNS, x = 0.2, 0.4, 0.6, 0.8) glass-ceramics were synthesized through the controlled crystallization method. The phase structure, dielectric and energy-storage properties were systematically studied through the Sr substitution for Ba. It was found that the dielectric properties were improved due to the formation of solid liquid phase Sr0.5Ba0.5Nb2O6. Breakdown strength firstly increases and then decreases, which strongly depends on the variation in interfacial polarization. The highest value of breakdown strength reaches 1828 ± 88 kV/cm for x = 0.4, which is attributed to more uniform and dense microstructure and lower interfacial polarization. Correspondingly, the optimized theoretical energy-storage density reaches up to 17.45 ± 0.74 J/cm3. The maximum of discharged energy-storage density of 1.45 J/cm3 from P-E loop was acquired under electric field of 500 kV/cm. Moreover, discharged power density of the capacitor was evaluated and reached a high value of 1.76 MV/cm3 in pulsed charged-discharged circuit.
Co-reporter:Shaohui Liu, Jiao Wang, Bo Shen, Jiwei Zhai, Haoshan Hao, Limin Zhao
Journal of Alloys and Compounds 2017 Volume 696(Volume 696) pp:
Publication Date(Web):5 March 2017
DOI:10.1016/j.jallcom.2016.11.186
•BaTiO3@Al2O3 nanofibers/PVDF nanocomposite films were prepared.•The discharged energy density performance of the nanocomposite films were investigated.•The discharged energy density of the nanocomposite films are enhanced compared with PVDF.•The enhancement mechanism of the nanocomposite films was proposed.BaTiO3@Al2O3 core-shell nanofibers (BT@Al2O3 NF) have been successfully synthesized. Homogeneous nanocomposites consisting of BT@Al2O3 NF and a Poly(vinylidene fluoride) (PVDF) polymer matrix have been prepared by the solution casting method. A systematic study was investigated on the effect of BT@Al2O3 NF filler introduction on the discharged energy density performance of the nanocomposite. Al2O3 shell dramatically reduces the leakage current by prevent the contact between BT NF fillers in nanocomposites and minimize the Maxwell-Wagner-Sillars interfacial polarization, which results in the enhancement of the breakdown strength of nanocomposites films. Simultaneously, the nanocomposites have higher maximum polarization and lower the remnant polarization than that of PVDF films under the same electric field. The maximum discharged energy density of the nanocomposites with 2.5 vol% BT@Al2O3 NF reaches 7.1 J/cm3 at 3800 kV/cm with an efficiency of above 65.1%. This work may provide an effective solution for enhancing the discharged energy density of nanocomposites films.
Co-reporter:Jinhua Liu, Haitao Wang, Bo Shen, Jiwei Zhai, Zhongbin Pan, Ke Yang, Jingran Liu
Journal of Alloys and Compounds 2017 Volume 722(Volume 722) pp:
Publication Date(Web):25 October 2017
DOI:10.1016/j.jallcom.2017.06.066
•The surface and inter crystallization mechanisms simultaneously occurred.•The microstructure and breakdown strength were improved.•The highest theoretical energy-storage density reached 15.3 J/cm3.•The energy efficiency increased from 74.2% to 91.5%.In this work, (100-x)(0.12 SrO-0.3 Na2O-0.1 Nb2O5)-xSiO2 (x = 30, 35, 40, 45, 50 mol%) glass-ceramics were prepared by using the meth-quenching-controlled crystallization method. Phase evolution, Crystallization mechanism, dielectric properties, dielectric breakdown strength (DBS), and energy-storage performances were comprehensively studied by varying SiO2 content. DSC studies revealed simultaneous occurrence of surface and internal crystallization mechanism in the glass-ceramics. XRD results showed three tungsten bronze structure SrNb2O6, Sr6Nb10O30, NaSr2Nb5O15 phases and perovskite structure NaNbO3 phase, which was quantified by the Reietveld refinement. It was found that dielectric constant and theoretical energy-storage density increased firstly and then decreased with the increase of the SiO2 contents. For x = 35 mol%, the theoretical energy-storage density reaches the maximal value of 15.3 J/cm3 due to the highest dielectric constant of 124 and DBS of 1669 kV/cm. And the highest DBS is related to the uniform and dense microstructure for x = 35 mol%. For practical applications in pulsed RLC circuit, the discharged efficiency increases from 74.2% to 91.5% with the increase of the SiO2 contents.
Co-reporter:Jiao Wang, Shaohui Liu, Jingyi Wang, Haoshan Hao, Limin Zhao, Jiwei Zhai
Journal of Alloys and Compounds 2017 Volume 726(Volume 726) pp:
Publication Date(Web):5 December 2017
DOI:10.1016/j.jallcom.2017.07.341
•SrTiO3@ PVP nanoparticles/PVDF nanocomposite films were prepared.•The energy density performance of the nanocomposite films were investigated.•The energy density of the nanocomposite films are enhanced compared with PVDF.•The enhancement mechanism of the nanocomposite films was proposed.Homogeneous nanocomposites flexible films is fabricated by incorporating surface modified paraelectric SrTiO3 nanoparticles (ST NP) by polyvinylpyrrolidone (PVP) into a polyvinylidene fluoride (PVDF) matrix. A systematic study was investigated on the effect of surface modified ST NP fillers on the dielectric properties and energy storage density of the nanocomposite films. Compared to pure PVDF, nanocomposite films with 5 vol % surface modified ST NP show a maximal energy density of 5.1 J/cm3, which is 182% higher than that of the pure PVDF. Moreover, the nanocomposites films exhibits a high efficiency of 80.7% at electric fields below 1000 kV/cm and still higher than 64.6% at an electric field of 2700 kV/cm. The results demonstrate that the nanocomposites films using the surface modified paraelectric fillers exhibit high energy storage densities and high efficiency.
Co-reporter:Wangfeng Bai, Daqin Chen, Peng Zheng, Jingji Zhang, Fei Wen, Bo Shen, Jiwei Zhai, Zhenguo Ji
Journal of Alloys and Compounds 2017 Volume 709(Volume 709) pp:
Publication Date(Web):30 June 2017
DOI:10.1016/j.jallcom.2017.03.185
•The switching characteristics of MPB compositions have been explored.•The correlation between phase evolution and electrical properties was studied.•A high strain of 0.34% with Smax/Emax = 486 p.m./V was achieved.•The source of high strain was unraveled.In this study, the switching characteristics of MPB compositions of (1-x-y)(Bi0.5Na0.5)TiO3-xKNbO3-ySrTiO3 (abbreviated as BNT-KN-ST) and temperature- and composition-driven strain behavior, dielectric, ferroelectric (FE), piezoelectric, and pyroelectric properties were systematically explored to achieve lead-free piezoelectric materials with large strain response for practical applications of piezoelectric actuators. The piezoelectric coefficient (d33) declined dramatically and normalized strain Smax/Emax increased markedly as the morphotropic phase boundary (MPB) compositions shifted away from the MPB (I) into the MPB (II) where the ferroelectric rhombohedral and relaxor pseudo-cubic phases coexisted at around critical composition. The critical compositions for the indicated system exhibited enhanced strain response, and at room temperature a high strain of 0.34% with normalized strain Smax/Emax = 486 p.m./V was gained for the critical composition 0.90BNT-0.05KN-0.05ST. The source of the achieved large strain was sought based on the X-ray diffraction (XRD) and Raman-spectra structure analysis, macroscopic properties, thermal depolarization progress, and temperature-dependent correlations of both polarization and strain, and the results indicated that it derived from the phase transformation contribution from ergodic relaxor (ER) to FE phases. Moreover, the present work also established the relationship between the MPB composition and tolerance factor t in BNT-based ceramics, and demonstrated that the t corresponding to the formation of MPB located in a quite narrow range. As a result, we believe that this study will open the door to quickly detect the approximate MPB region for BNT-based solid solutions.
Co-reporter:Zhongbin Pan, Lingmin Yao, Jiwei Zhai, Bo Shen, Haitao Wang
Composites Science and Technology 2017 Volume 147(Volume 147) pp:
Publication Date(Web):28 July 2017
DOI:10.1016/j.compscitech.2017.05.004
Flexible dielectric polymeric films are highly desirable materials with potential applications in power-conditioning equipment and pulsed-plasma thrusters due to their high dielectric constant, low dielectric loss, and fast energy uptake and delivery. In this work, 1–3 type nanocomposites combining BaTiO3 nanotubes (BT NTs) and poly(vinylidene fluoride) (PVDF) were prepared by a solution cast method. The BT NTs were synthesized by facile coaxial electrospinning and were coated with a dense and robust dopamine layer, which effectively improved the filler-matrix distributional homogeneity and compatibility. The 10.8 vol% BT-DA NTs/PVDF nanocomposites possessed an excellent dielectric constant of 47.05, which is approximately 569% greater that of the pristine PVDF (8.26) and 150%–350% higher than that of the other PVDF nanocomposites loaded with similar ceramic filler contents, e.g., nanoparticles, nanowires, and nanofibers. The highest energy density of 7.03 J cm−3 at a relatively low field of 330 MV m-1 was obtained via small loaded of the fillers, which is approximately 625% greater than for biaxially oriented polypropylenes (BOPP) (1.2 J cm−3 at the field of 640 MV m−1). The approach employed in this study may be further applied to the fabrication of similar polymeric nanocomposites for next-generation electronic components.
Co-reporter:Baihui Liu, Peng Li, Bo Shen, Jiwei Zhai, ... Xing Liu
Ceramics International 2017 Volume 43, Issue 11(Volume 43, Issue 11) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.ceramint.2017.03.090
In this study, <001>-textured 0.99(K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O3−0.01CaZrO3 [abbreviated as 0.99KNLNS-0.01CZ] lead-free ceramics were prepared by templated grain growth (TGG) using plate-like NaNbO3 templates and sintered by a two-step sintering process with different soaking time. All textured samples with high Lotgering factor (f >85%) presented orthorhombic and tetragonal coexisting phase, and the proportion of orthorhombic phase was varied with prolonged soaking time. A large piezoelectric constant d33 (~ 310 pC/N) was obtained in the textured samples with a 12 h soaking time, which was almost twice larger compared to the randomly oriented one. Furthermore, the field-induced piezoelectric strain coefficient d33*(~ 440 pm/V) of the textured ceramics with 6 h soaking time was larger than the value of randomly oriented one (~ 298 pm/V) at room-temperature. Enhanced piezoelectric response and good temperature stability prove that <001>-textured 0.99KNLNS-0.01CZ ceramics are promising candidates in the field of lead-free piezoelectric materials.
Co-reporter:Haitao Wang, Jinhua Liu, Jiwei Zhai, Bo Shen, ... Ke Yang
Ceramics International 2017 Volume 43, Issue 12(Volume 43, Issue 12) pp:
Publication Date(Web):15 August 2017
DOI:10.1016/j.ceramint.2017.04.026
The SrO-Na2O-Nb2O5-SiO2 (SNNS) glass-ceramics were prepared through the melt-quenching combined with the controlled crystallization technique. XRD results showed Sr6Nb10O30, SrNb2O6, NaSr2Nb5O15 with tungsten bronze structure and NaNbO3 with the perovskite structure. With the decrease of crystallization temperature, dielectric constant firstly increased and then decreased, while breakdown strength (BDS) was increased. High BDS of the glass-ceramics is attributed to the dense and uniform microstructure at low crystallization temperature. The optimal dielectric constant of 140±7 at 900 °C and BDS of 2182±129 kV/cm at 750 °C were obtained in SNNS glass-ceramics. The theoretical energy-storage density was significantly improved up to the highest value of 15.2±1.0 J/cm3 at 800 °C, which is about 5 times than that at 950 °C. The discharged efficiency increased from 65.8% at 950 °C to 93.6% at 750 °C under the electric field of 500 kV/cm by decreasing crystallization temperature.
Co-reporter:Pan Chen, Peng Li, Jiwei Zhai, Bo Shen, ... Shuanghao Wu
Ceramics International 2017 Volume 43, Issue 16(Volume 43, Issue 16) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.ceramint.2017.07.039
Lead free Bi0.5(Na0.8K0.2)0.5TiO3 thin films doped with BiFeO3 (abbreviated as BNKT-xBFO) (x = 0, 0.02, 0.04, 0.08, 0.10) were deposited on Pt(111)/Ti/SiO2/Si substrates by sol-gel/spin coating technique and the effects of BiFeO3 content on the crystal structure and electrical properties were investigated in detail. The results showed that all the BNKT-xBFO thin films exhibited a single perovskite phase structure and high-dense surface. Reduced leakage current density, enhanced dielectric and ferroelectric properties were achieved at the optimal composition of BNKT-0.10BFO thin films, with a leakage current density, dielectric constant, dielectric loss and maximum polarization of < 2 × 10−4 A/cm3, ~ 978, ~ 0.028 and ~ 74.13 μC/cm2 at room temperature, respectively. Moreover, the BNKT-0.10BFO thin films possessed superior energy storage properties due to their slim P-E loops and large maximum polarization, with an energy storage density of 22.12 J/cm3 and an energy conversion efficiency of 60.85% under a relatively low electric field of 1200 kV/cm. Furthermore, the first half period of the BNKT-0.10BFO thin film capacitor was about 0.15 μs, during which most charges and energy were released. The large recoverable energy density and the fast discharge process indicated the potential application of the BNKT-0.10BFO thin films in electrostatic capacitors and embedded devices.
Co-reporter:Lingmin Yao;Zhongbin Pan;Haydn H. D. Chen
Nanoscale (2009-Present) 2017 vol. 9(Issue 12) pp:4255-4264
Publication Date(Web):2017/03/23
DOI:10.1039/C6NR09250K
Nanocomposites in capacitors combining highly aligned one dimension ferroelectric nanowires with polymer would be more desirable for achieving higher energy density. However, the synthesis of the well-isolated ferroelectric oxide nanorod arrays with a high orientation has been rather scant, especially using glass-made substrates. In this study, a novel design that is capable of fabricating a highly [110]-oriented BaTiO3 (BT) nanorod array was proposed first, using a three-step hydrothermal reaction on glass-made substrates. The details for controlling the dispersion of the nanorod array, the orientation and the aspect ratio are also discussed. It is found that the alkaline treatment of the TiO2 (TO) nanorod array, rather than the completing transformation into sodium titanate, favors the transformation of the TO into the BT nanorod array, as well as protecting the glass-made substrate. The dispersity of the nanorod array can be controlled by the introduction of a glycol ether-deionized water mixed solvent and soluble salts. Moreover, the orientation of the nanorod arrays could be tuned by the ionic strength of the solution. This novel BT nanorod array was used as a filler in a nanocomposite capacitor, demonstrating that a large energy density (11.82 J cm−3) can be achieved even at a low applied electric field (3200 kV cm−1), which opens us a new application in nanocomposite capacitors.
Co-reporter:Zhongbin Pan;Bo Shen
Journal of Materials Chemistry A 2017 vol. 5(Issue 29) pp:15217-15226
Publication Date(Web):2017/07/25
DOI:10.1039/C7TA03846A
Polymer nanocomposites with high energy density have potential applications in advanced electronics and electric power systems. The inevitable electrical mismatch between nanofillers and the polymer matrix could compromise the energy storage capability and dielectric properties of the polymer nanocomposites. Herein, novel core–double-shell structured BaTiO3@TiO2@Al2O3 nanofibers (BT@TO@AO NFs) were prepared via a one step method, and were incorporated into poly(vinylidene fluoride) (PVDF). The novel design of gradually varying the multilayer hierarchical interface was advantageous to alleviating the local electric field and electric current density intensification in the filler/polymer system. As compared with the nanocomposites loaded with BT NFs and BT@TO NFs, the nanocomposites filled with BT@TO@AO NFs exhibit much decreased dielectric loss, enhanced breakdown strength, and suppressed leakage current densities. Simulations were carried out to verify that the new core–double-shell structure significantly enhances the breakdown strength and energy density. As a result, the nanocomposite films loaded with 3.6 vol% BT@TO@AO NFs show a maximum energy storage density (Ue) of 14.84 J cm−3 at 450 MV m−1, which is about twelve times greater than that of biaxially oriented polypropylene (BOPP) (≈1.2 J cm−3 at 640 MV m−1). Moreover, the nanocomposite exhibits a superior power density of 4.7 MW cm−3 and an ultra-fast discharge speed of 0.37 μs. This research opens up a convenient and effective way for designing high-performance dielectric polymer nanocomposites.
Co-reporter:Wangfeng Bai;Peng Zheng;Fei Wen;Jingji Zhang;Daqin Chen;Zhenguo Ji
Dalton Transactions 2017 vol. 46(Issue 44) pp:15340-15353
Publication Date(Web):2017/11/14
DOI:10.1039/C7DT02846F
The development of (Bi0.5Na0.5)TiO3-based solid solutions with both high depolarization temperature Td and excellent piezoelectric and electromechanical properties for practical application is intractable because improved thermal stability is usually accompanied by a deterioration in piezoelectric and electromechanical performance. Herein, we report a 0–3 type 0.93(Bi0.5Na0.5)TiO3–0.07BaTiO3 : 30 mol%ZnO composite (BNT-7BT : 0.3ZnO), in which the ZnO nanoparticles exist in two forms, to resolve the abovementioned long-standing obstacle. In this composite, Zn ions fill the boundaries of BNT-7BT grains, and residual Zn ions diffuse into the BNT-7BT lattice, as confirmed by XRD, Raman spectroscopy, and microstructure analysis. The BNT-7BT composite ceramics with a 0–3 type connectivity exhibited enhanced frequency-dependent electromechanical properties, fatigue characteristics, and thermal stabilities. More importantly, low poling field-driven large piezoelectric properties were observed for the composite ceramics as compared to the case of the pure BNT-7BT solid solution. A mechanism related to the ZnO-driven phase transition from the rhombohedral to tetragonal phase and built-in electric field to partially compensate the depolarization field was proposed to explain the achieved outstanding piezoelectric performance. This is the first time that the thermal stability, electromechanical behavior, and low poling field-driven high piezoelectric performance of BNT-based ceramics have been simultaneously optimized. Thus, our study provides a referential methodology to achieve novel piezoceramics with excellent piezoelectricity by composite engineering and opens up a new development window for the utilization of conventional BNT-based and other lead-free ceramics in practical applications.
Co-reporter:Xing Liu, Feng Li, Peng Li, Jiwei Zhai, ... Baihui Liu
Journal of the European Ceramic Society 2017 Volume 37, Issue 15(Volume 37, Issue 15) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.jeurceramsoc.2017.05.042
In this study, the Bi-nonstoichiometric 0.99Bix(Na0.8K0.2)0.5TiO3-0.01SrTiO3 (BNKST) ceramics with x = 0.5–0.535 mol (Bi50-Bi53.5) were prepared by a conventional solid-state reaction method. The effects of Bi excess on structural transition and ferroelectric stability of BNKST ceramics were systematically investigated by the Raman spectra, dielectric analyses and electromechanical measurements. The introduction of excess Bi3+ could significantly break the long-range ferroelectric order and favor the presence of relaxor phase, then the ferroelectric-relaxor transition temperature (TFR) can be effectively tuned to around room temperature by Bi nonstoichiometry, giving rise to an enhanced room-temperature strain property. The positive strain Spos and dynamic piezoelectric constant d33* of Bi52.5 critical composition reach 0.33% and 440 pm/V, respectively at 6 kV/mm. The high recoverable strain of Bi52.5 sample can be attributed to the electric-field-induced reversible relaxor-ferroelectric phase transition. The present work may be helpful for further understanding and designing high-performance NBT-based lead-free ceramics for piezoelectric actuator applications.
Co-reporter:Zhongbin Pan, Lingmin Yao, Jiwei Zhai, Bo Shen, Shaohui Liu, Haitao Wang and Jinhua Liu
Journal of Materials Chemistry A 2016 vol. 4(Issue 34) pp:13259-13264
Publication Date(Web):10 Aug 2016
DOI:10.1039/C6TA05233A
Inorganic/polymer nanocomposites, using one-dimensional (1D) core–shell structure BaTiO3@Al2O3 nanofibers (BT@Al2O3 nfs) as fillers and poly(vinylidene fluoride) (PVDF) as the polymer matrix, have been prepared. The core–shell structure BT@Al2O3 nfs have been synthesized via coaxial electrospinning. The breakdown strength (Eb) and discharged energy density of the nanocomposites can be significantly improved by creating an insulating Al2O3 shell layer with moderate dielectric constant on the surfaces of BT nanofibers to form a moderate interfacial area. The Al2O3 shell layer could effectively confine the mobility of charge carriers, which reduces energy loss by reducing the Maxwell–Wagner–Sillars (MWS) interfacial polarization and space charge polarization between the fillers and the polymer matrix. As a result, the nanocomposite films filled with 5 vol% BT@Al2O3 nfs exhibit a excellent discharge energy density of 12.18 J cm−3 at 400 MV m−1, which is ≈254% over bare PVDF (4.8 J cm−3 at 350 MV m−1) and ≈1015% greater than the biaxially oriented polypropylenes (BOPP) (≈1.2 J cm−3 at 640 MV m−1). The work here indicates that this promising state-of-the-art method of preparing high energy density nanocomposites can be used in the next generation of dielectric capacitors.
Co-reporter:Lingmin Yao, Zhongbin Pan, Shaohui Liu, Jiwei Zhai, and Haydn H. D. Chen
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 39) pp:26343
Publication Date(Web):September 13, 2016
DOI:10.1021/acsami.6b09265
A novel inorganic/polymer nanocomposite, using 1-dimensional TiO2 nanorod array as fillers (TNA) and poly(vinylidene fluoride) (PVDF) as matrix, has been successfully synthesized for the first time. A carefully designed process sequence includes several steps with the initial epitaxial growth of highly oriented TNA on the fluorine-doped tin oxide (FTO) conductive glass. Subsequently, PVDF is embedded into the nanorods by the spin-coating method followed by annealing and quenching processes. This novel structure with dispersive fillers demonstrates a successful compromise between the electric displacement and breakdown strength, resulting in a dramatic increase in the electric polarization which leads to a significant improvement on the energy density and discharge efficiency. The nanocomposites with various height ratios of fillers between the TNA and total film thickness were investigated by us. The results show that nanocomposite with 18% height ratio fillers obtains maximum increase in the energy density (10.62 J cm–3) at a lower applied electric field of 340 MV m–1, and it also illustrates a higher efficiency (>85%) under the electric field less than 100 MV m–1. Even when the electric field reached 340 MV m–1, the efficiency of nanocomposites can still maintained at ∼70%. This energy density exceeds most of the previously reported TiO2-based nanocomposite values at such a breakdown strength, which provides another promising design for the next generation of dielectric nanocomposite material, by using the highly oriented nanorod array as fillers for the higher energy density capacitors. Additionally, the finite element simulation has been employed to analyze the distribution of electric fields and electric flux density to explore the inherent mechanism of the higher performance of the TNA/PVDF nanocomposites.Keywords: capacitors; energy density; nanocomposites; nanorod arrays; poly(vinylidene fluoride); titanium oxides
Co-reporter:Wangfeng Bai, Daqin Chen, Peng Zheng, Bo Shen, Jiwei Zhai and Zhenguo Ji
Dalton Transactions 2016 vol. 45(Issue 20) pp:8573-8586
Publication Date(Web):13 Apr 2016
DOI:10.1039/C6DT00906A
In this study, a lead-free ceramic system comprising (0.94 − x)Bi0.5Na0.5TiO3–0.06BaTiO3–xBi(Zn0.5Ti0.5)O3 (BNT–BT–BZT) was designed and prepared by a conventional solid-state reaction method. The effect of the addition of BZT on the phase transition characteristics and associated electromechanical properties of BNT–BT was systematically discussed and a schematic phase diagram was established. The addition of BZT had a strong impact on the phase transition as well as the strain and piezoelectric activity. The phase coexistence, which involves ferroelectric rhombohedral-relaxor pseudocubic phases, can be driven by modification with BZT and increases in temperature and can be confirmed by XRD measurements, analysis of Raman spectra and temperature-dependent changes in polarization and strain hysteresis loops. Accompanied by a shift in the ferroelectric-to-relaxor temperature TF–R to below room temperature on the addition of BZT, a compositionally induced ferroelectric-to-relaxor phase transition occurred, which gave rise to a large strain of 0.33% with a normalized strain Smax/Emax of 550 pm V−1 at the critical BZT content x of 0.0275. The results were closely correlated with the composition and dependence on temperature of the phase transition, which significantly influenced the electromechanical properties, and the origin of the large strain observed in the present system was also addressed in detail. As a result, the design principles provided in this study open the possibility of obtaining BNT-based lead-free ceramics with enhanced electromechanical properties for actuator applications.
Co-reporter:Shi Xiao, Shaomei Xiu, Bo Shen, Jiwei Zhai
Journal of the European Ceramic Society 2016 Volume 36(Issue 16) pp:4071-4076
Publication Date(Web):December 2016
DOI:10.1016/j.jeurceramsoc.2016.06.044
The potassium strontium niobate boroaluminosilicate (KSN-BAS) glass-ceramics were prepared through microwave sintering. The effects of crystallization time on the microstructure and dielectric properties of the KSN-BAS glass-ceramics were investigated. The XRD results exhibited that an impure phase AlNbO4 was devitrified from the glass matrix as the crystallization time increased. The microstructure showed that the grain size increased as the crystallization time prolonged. Crystal boundary activation energy of the KSN-BAS glass-ceramics was performed by impedance analysis. The dielectric constant and electric breakdown strength indicated a trend of increasing at first and then reducing with the increase of the crystallization time. When the crystallization time was 10 min, the optimization of dielectric constant of 102.0 and breakdown strength of 1410.81 kV/cm were obtained. The maximum of theoretical energy storage density can reach a value of 8.99 J/cm3. For pulsed power applications, the discharge efficiency and power density were evaluated by RLC circuit.
Co-reporter:Haitao Wang, Jinhua Liu, Jiwei Zhai, Bo Shen, Shaomei Xiu, Shi Xiao, Zhongbin Pan
Journal of Alloys and Compounds 2016 Volume 687() pp:280-285
Publication Date(Web):5 December 2016
DOI:10.1016/j.jallcom.2016.06.024
•A high breakdown strength of 2074 kV/cm was obtained in the strontium sodium niobate-based glass ceramics.•The energy storage density succeeds in a high value 10.09 J/cm3.•The discharge behavior of the capacitor was studied.•The discharge efficiency of the capacitor reaches 90.1%.The niobate-based glass-ceramics with a high energy storage density were prepared by using the controlled crystallization technology in the (Na2O, SrO)Nb2O5SiO2 glass-ceramics. The dielectric properties, energy storage density, and discharge properties were investigated with the variation of the Na/Sr molar ratio. By varying the Na/Sr ratio, the energy storage density raises up to a high value of 10.09 J/cm3. With the variation of the Na/Sr ratio, both dielectric breakdown strength and discharge efficiency have an opposite change trend with the activation energy that reflects the interface polarization of the glass-ceramics. In contrast, for Na/Sr = 1/2, the glass-ceramic has the lower activation energy, which indicates that its interfacial polarization is weaker due to a fine microstructure. Thus, the glass-ceramics for Na/Sr = 1/2 have the characteristics of the higher breakdown strength of 2074 kV/cm and the higher discharge efficiency of 90.1%. Then it may contribute to the high energy storage density capacitor.
Co-reporter:Wangfeng Bai, Daqin Chen, Peng Li, Bo Shen, Jiwei Zhai, Zhenguo Ji
Ceramics International 2016 Volume 42(Issue 2) pp:3429-3436
Publication Date(Web):1 February 2016
DOI:10.1016/j.ceramint.2015.10.139
<001>-textured (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT) lead-free piezoelectric ceramics were fabricated by templated grain growth using plate-like BaTiO3 as template. The effects of <001> orientation degree on the microstructure and resulting changes in dielectric, ferroelectric, piezoelectric, and strain properties were systematically investigated to develop the lead-free piezoelectric materials with an excellent actuating performance. The electromechanical properties were found to increase monotonously with the increase in the degree of texturing and dramatically enhanced for the textured BCZT ceramics in the optimized microstructure compared with randomly-oriented counterparts. Highly textured ceramics showed excellent electromechanical properties of d33=462 pC/N, kp=47%, S=0.187%, and Smax/Emax=621 pm/V at room temperature. These results indicates that the textured ceramics are promising candidates for environmentally friendly actuator devices with high performance.
Co-reporter:Wangfeng Bai, Daqin Chen, Jingji Zhang, Jiasong Zhong, Mingye Ding, Bo Shen, Jiwei Zhai, Zhenguo Ji
Ceramics International 2016 Volume 42(Issue 2) pp:3598-3608
Publication Date(Web):1 February 2016
DOI:10.1016/j.ceramint.2015.11.023
Lead-free (Ba0.85Ca0.15)(ZrxTi1−x)O3 (BCZT,0.03≤x≤0.25) ceramics were synthesized in a wide compositional range to investigate the relationship between its phase diagram and electromechanical properties. The effects of Zr content on microstructure, phase transition behavior, ferroelectric, dielectric, piezoelectric and strain properties of BCZT ceramics were systemically studied. The morphotropic phase boundary (MPB) of BCZT ceramics was closely connected with the presence of orthorhombic phase between rhombohedral and tetragonal phases at a narrow region, which could meet in a region that is termed the diffuse ferroelectric phase transition region (DPTR) in this work. As a result, the composition x=0.08 located at near MPB region close to tetragonal phase side exhibited the outstanding electrical behavior at room temperature: d33=349 pC/N, kp=43%, S=0.185% and Smax/Emax=463 pm/V. Furthermore, pure electrostrictive effect with large electrostrictive coefficient Q11 of 0.036 m4 C−2 had also been observed in the composition x=0.20, and large Q11 of MPB composition showed superior temperature stability in the investigated temperature range.
Co-reporter:Peng Li, Jiwei Zhai, Huarong Zeng, Bo Shen, Wei Li, Kunyu Zhao
Journal of the European Ceramic Society 2016 Volume 36(Issue 13) pp:3139-3145
Publication Date(Web):October 2016
DOI:10.1016/j.jeurceramsoc.2016.05.019
To attain a deep understanding of piezoelectric and dielectric properties dependence of crystallographic orientation, the rhombohedral 0.90(Bi0.5Na0.5)TiO3-0.10(Bi0.5K0.5)TiO3 (abbreviated as BNT-BKT) single-crystal films with three primary orientations of (100), (110), (111) were obtained by sol-gel method. Crystallographic structure measurement by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) revealed that the BNT-BKT films display a pure perovskite phase and a good epitaxial relationship. Crystallographic orientation dependence of piezoelectric and dielectric properties of the BNT-BKT thin films was investigated. The superior piezoelectric properties in (100)-oriented epitaxial thin films are mainly derived from the intrinsic piezoelectric activities based on the crystallographic orientation and corresponding ferroelectric domain structure analysis. It is also important to note that the Curie temperature (Tc) and dielectric permittivity in piezoelectric films were also affected by the crystallographic orientation.
Co-reporter:Baihui Liu, Yang Zhang, Peng Li, Bo Shen, Jiwei Zhai
Ceramics International 2016 Volume 42(Issue 12) pp:13824-13829
Publication Date(Web):September 2016
DOI:10.1016/j.ceramint.2016.05.186
Abstract
In this work, (1−x)(K0.52Na0.48)Nb0.95Sb0.05O3−xBi0.5(Na0.8K0.2)0.5ZrO3 [abbreviated as (1−x)KNNS−xBNKZ, x=0–0.06] lead-free ceramics were fabricated using solid-state reaction method. The effects of BNKZ contents on the phase structure, piezoelectric and ferroelectric properties were investigated. The phase boundaries including orthorhombic-tetragonal (O-T) and rhombohedral-tetragonal (R-T) multiphase coexistence were identified by XRD patterns and temperature-dependent dielectric constant by adding different content of BNKZ. A giant field induced strain (~0.25%) along with converse piezoelectric coefficient d33* (~629.4 pm/V) and enhanced ferroelectricity Pr (~38 μC/cm2) were obtained when x=0.02, while the specimen with x=0.03 presented the optimal piezoelectric coefficient d33 of 215 pC/N, due to the O-T or R-T phase coexistence near room temperature respectively. These results show that the introduction of Bi0.5(Na0.8K0.2)0.5ZrO3 is a very effective way to improve the electrical properties of (K0.52Na0.48)(Nb0.95Sb0.05)O3 lead-free piezoelectric ceramics.
Co-reporter:Z.B. Pan, L.M. Yao, J.W. Zhai, S.H. Liu, K. Yang, H.T. Wang, J.H. Liu
Ceramics International 2016 Volume 42(Issue 13) pp:14667-14674
Publication Date(Web):October 2016
DOI:10.1016/j.ceramint.2016.06.090
Abstract
Nanocomposites combining high breakdown strength (BDS) polymer and high dielectric permittivity ceramic fillers have shown great potential for pulsed power application. Here a new composite material based on surface-functionalized Ba0.6Sr0.4TiO3 nanofibers/poly(vinylidene fluoride) (BST NF/PVDF) has been prepared by solution casting. The nanocomposites containing 2.5 vol% isopropyl dioleic(dioctylphosphate) titanate (NDZ 101)-functionalized BST NF (N-h-BST NF) have large energy density of 6.95 J cm−3 at 380 MV m−1, which is 1.85 times larger than that of the pure PVDF at the same electric field. Also, the discharge speed of the nanocomposites containing 7.5 vol% N-h-BST NF is approximately 0.11 μs. The good properties, together with the large energy density and fast discharge speed, make this material a promising candidate for pulsed power capacitor.
Co-reporter:Shi Xiao, Shaomei Xiu, Wenqing Zhang, Bo Shen, Jiwei Zhai, Yang Zhang
Journal of Alloys and Compounds 2016 Volume 675() pp:15-21
Publication Date(Web):5 August 2016
DOI:10.1016/j.jallcom.2016.03.105
•The maximum energy storage density of the BST composites increases to 3.1 J/cm3.•The dielectric constant can be increased from 56 to 611 as the BST ceramic added.•The microstructure is modified by adding an appropriate content of BST ceramics.•The BDS of the samples synthesized by ceramic and glass-ceramic can be improved.•The relationship between breakdown strength and dielectric constant is studied.A series of Ba0.4Sr0.6TiO3–BaO–B2O3–Al2O3–SiO2 (BST40-BBAS) glass-ceramics with different content of BaxSr1−xTiO3 (x = 0.4, 0.7 and 0.9) additives were synthesized by solid state sintering process. The relationships between phase structure, microstructure and dielectric properties were investigated. The XRD results illustrated that all the peaks of BST phases shifted to lower angle with the increasing of BaxSr1−xTiO3 additives. Moreover, the shift tendency of peaks became more obvious as the x increased. The microstructure results exhibited that an appropriate composition of BaxSr1−xTiO3 additives could cut off the contact among the BST glass powders, which effectively restrained the abnormal growth of the BST glass-ceramics. As the BaxSr1−xTiO3 additives increased, the dielectric constant of the glass-ceramics increased from 56 to 611 and the Curie temperatures of the BST glass-ceramic specimens moved to high temperature. The breakdown strength (BDS) reduced from 853 kV/cm to 405 kV/cm with the increase of BST ceramics concentration. In order to obtain a maximum energy density, the relationship between dielectric breakdown strength and dielectric constant was studied. The glass-ceramic composites synthesized by BST40-BBAS glass-ceramic and BaxSr1−xTiO3 ceramics could effectively improve the energy storage density. A maximum of the calculated energy density reached up to 3.1 J/cm3, which was improved by 1.8 times as compared with that of the pure BST40-BBAS glass-ceramic (1.74 J/cm3).
Co-reporter:Wangfeng Bai, Daqin Chen, Yanwei Huang, Bo Shen, Jiwei Zhai, Zhenguo Ji
Journal of Alloys and Compounds 2016 Volume 667() pp:6-17
Publication Date(Web):15 May 2016
DOI:10.1016/j.jallcom.2016.01.144
•Structure and electromechanical properties of BNT-BT-xBA system were investigated.•Ferroelectric-relaxor phase transition at room temperature was identified.•A large strain of 0.37% with Smax/Emax = 533 pm/V was obtained at x = 0.02.•The underlying mechanism of enhanced strain response has been explored.Ternary solid solution of (0.94-x) Bi0.5Na0.5TiO3-0.06BaTiO3-xBiAlO3 (BNT-BT-BA) lead-free piezoceramics was prepared using solid state reaction. Effect of BiAlO3 addition to Bi0.5Na0.5TiO3–BaTiO3 ceramics on structure, phase stability, strain behavior, dielectric, ferroelectric, pyroelectric, and piezoelectric properties was systematically investigated and a schematic phase diagram was proposed based on the phase transition temperature. The correlation between ferroelectric-to-relaxor transition temperature TF-R and depolarization temperature Td was shown by the comparison with Td determined by thermally stimulated depolarization current measurements and TF-R obtained from dielectric results, and investigated by temperature-dependent the stability of electrically induced long-range ferroelectric order and piezoelectricity. Accompanied with the TF-R shifted down below room temperature as the substitution of BiAlO3, electric-field-induced long-range ferroelectric order was disrupted, giving rise to a large strain of 0.37% with normalized strain Smax/Emax = 533 pm/V at a critical composition x of 0.02. Temperature-dependent changes in polarization and strain hysteresis loops in combination with XRD measurements and Raman-spectra analysis suggested that the large strain response should be attributed to the electric-field-induced phase transformation between ergodic relaxor and ferroelectric phase.
Co-reporter:Wangfeng Bai, He Li, Junhua Xi, Jingji Zhang, Bo Shen, Jiwei Zhai
Journal of Alloys and Compounds 2016 Volume 656() pp:13-23
Publication Date(Web):25 January 2016
DOI:10.1016/j.jallcom.2015.09.209
•BNT and ST template particles with uniform microstructure were prepared.•Effects of BNT and ST templates on structure and strain behavior were investigated.•Effects of texture on structure evolution and strain response were explored.•A large strain of 0.38% with Smax/Emax = 540 pm/V was obtained for sample with BNT.•The sample with BNT exhibited enhanced temperature stability compared to random one.In this work, <001> oriented 0.90(Bi0.5Na0.5)TiO3–0.05KNbO3–0.05SrTiO3 (BNT–KN–ST) ceramics with high degree of texturing were produced by templated grain growth using different perovskite plate-like (Bi0.5Na0.5)TiO3 and SrTiO3 as template particles. The effects of different template particles on the grain orientation, structure evolution, phase stability and strain response was systematically investigated to develop the lead-free piezoelectric materials with an excellent actuating performance. The strain response increased monotonously with the increase in the degree of texturing and the optimized microstructure was found to provide excellent strain properties with a large strain of 0.38% and normalized strain Smax/Emax = 540 pm/V for the textured samples with BNT template particles at room temperature as compared to the random counterparts. The temperature-dependent strain response is also compared to randomly oriented ceramics and the results demonstrated that the textured piezoceramics with BNT template particles exhibited the enhancement in the temperature stability over the temperature range room temperature-120 °C.
Co-reporter:Ruirui Liu, Zifang He, Jiwei Zhai, Sannian Song, Zhitang Song, Xiao Zhou
Materials Letters 2016 Volume 163() pp:20-23
Publication Date(Web):15 January 2016
DOI:10.1016/j.matlet.2015.10.036
•S18 film mainly contributes to quicken the phase-change speed of the film.•S2 film can increase the stability and lower the power consumption of the film.•[S18(2nm)-S2(10nm)]4 film shows the best properties.•The highest Tc is 200 °C with better data retention capability (112 °C) than GST.•The fastest phase-change speed of the film is 5 ns compared with 100 ns of GST.Superlattice-like Sn18Sb82–SnSe2 multiple thin films are systematically investigated for phase change memory application. The thin films have a preferable thermal stability owing to the wide bandgap, strong Sn–Se bond energy and the vacancies and local distortions existed in SnSe2. Besides, the variation in resistance of the film not only can lower the power consumption but also can facilitate device operation. Meanwhile, operating speed of the device based on specific [Sn18Sb82(2 nm)–SnSe2(10 nm)]4 thin film is dramatically increased, reaching 5 ns compared with 100 ns of traditional Ge2Sb2Te5. This high operating speed is mainly derived from the precipitated Sb phase and weak Sb–Sb, Se–Se bonds.
Co-reporter:Wei Li, Peng Li, Huarong Zeng, Zhenxing Yue, Jiwei Zhai
Materials Letters 2016 Volume 162() pp:135-137
Publication Date(Web):1 January 2016
DOI:10.1016/j.matlet.2015.09.137
•BNT–BT–ST films with systematic changed stress were prepared by sol–gel process.•Stress effect the electric properties by in-plane polarization and phase transition.•Excellent piezoelectric responses are obtained in the thin films with tensile stress.The Bi0.5Na0.5TiO3–BaTiO3–SrTiO3 (BNT–BT–ST) thin films were grown on the LaNiO3 buffered MgO, SrTiO3 and LaAlO3 single crystal substrates, respectively. A systematic stress change of the thin films was obtained. The effect of increasing tensile stress on phase transition temperature is attributed to the suppression of in-plane polarization. The tensile stress reduces the unit cell along electric field, remnant polarization and dielectric permittivity, while enhances the piezoelectric response in this study. The high strain level (0.25%) and piezoelectric coefficient (d33*=200 pm/V) were obtained. These results suggest that the piezoelectric properties of BNT–BT–ST thin films can be adjusted by choosing different stress magnitude.
Co-reporter:Shaohui Liu and Jiwei Zhai
Journal of Materials Chemistry A 2015 vol. 3(Issue 4) pp:1511-1517
Publication Date(Web):11 Nov 2014
DOI:10.1039/C4TA04455J
Compared to the spherical ceramic fillers, the one-dimensional ceramic fillers are more effective in enhancing the dielectric constant of the composites at low concentration because the depolarization factor is strongly dependent on the aspect ratio of the fillers. Moreover, their smaller specific surface can help to reduce the surface energy and thus prevent the nanofillers from agglomerating in the polymer matrix. The ceramic–polymer composites consisting of SrTiO3 nanofibers (ST NF) with a large aspect ratio prepared via electrospinning and modified by polyvinylpyrrolidone (PVP) as fillers and poly(vinylidene fluoride) (PVDF) as matrix have been fabricated by a solution casting method. The composites exhibit enhanced dielectric constant and reduced loss tangents at a low volume fraction of surface-modified ST NF. The composite containing 2.5 vol% of PVP modified ST NF exhibits an energy density as high as 6.8 J cm−3 at 3800 kV cm−1, which is more than double of the pure PVDF of 2.8 J cm−3 at 4000 kV cm−1. Moreover, the efficiency of the composites with 2.5 vol% PVP modified ST NF is higher than 85% at electric fields below 1000 kV cm−1 and still higher than 60% at an electric field of 3800 kV cm−1. Such significant enhancement is closely related to combined effects of the surface modification, large aspect ratio and paraelectric behavior of the ST NF.
Co-reporter:Lingyu Li, Yang Zhang, Wangfeng Bai, Bo Shen, Jiwei Zhai and Haydn Chen
Dalton Transactions 2015 vol. 44(Issue 25) pp:11621-11625
Publication Date(Web):20 May 2015
DOI:10.1039/C5DT01414J
Plate-like NaNbO3 (NN) templates have been successfully synthesized via a two-step molten salt method using K2CO3 as a raw material at 970 °C, which is below the topochemical reaction temperature using Na2CO3 as the raw material (higher than 1000 °C). The synthesized plate-like NN particles have a higher aspect ratio with a thickness of 0.5–1 μm, a width of 5–10 μm and a length of 15–25 μm. In this process, we found that Na2CO3 or K2CO3 plays an important role in removing the (Bi2O2)2+ layers in the substitution process and the final composition is decided by the type of molten salt. Using KCl as molten salt and Na2CO3 or K2CO3 as raw material, the (Bi2O2)2+ layers could be removed by Na2CO3 or K2CO3 and K+ ions can be incorporated into the template during the topochemical reaction and thus (K, Na)NbO3 (KNN) plate-like particles can be fabricated. The growth process is reasonably elucidated by this growth mechanism.
Co-reporter:Yang Zhang, Lingyu Li, Bo Shen and Jiwei Zhai
Dalton Transactions 2015 vol. 44(Issue 17) pp:7797-7802
Publication Date(Web):18 Mar 2015
DOI:10.1039/C5DT00593K
(1 − x)(K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O3-xSrZrO3 ((1 − x)KNLNS-xSZ) lead free piezoelectric ceramics have been prepared by the conventional solid state reaction method, via adjusting the orthorhombic–tetragonal phase transition temperature to near room temperature with doping SrZrO3, and the effects of SrZrO3 content on polymorphic phase transition have been investigated. These results show that the phase structure of the ceramics was changed from orthorhombic to tetragonal at x ≥ 0.02 mol, and the orthorhombic–tetragonal phase transition temperature was modified to around room temperature with increasing SrZrO3. Remarkable piezoelectric and ferroelectric properties has been obtained in (1 − x)KNLNS-xSZ system with x = 0.02, which showed a piezoelectric parameter of d33 = 256 pC N−1, Curie temperature Tc = 270 °C, strain levels of 0.16% at 50 kV cm−1, remnant polarization Pr = 24.9 μC cm−2 and coercive field Ec = 10.6 kV cm−1.
Co-reporter:Yang Zhang, Lingyu Li, Wangfeng Bai, Bo Shen, Jiwei Zhai and Bo Li
RSC Advances 2015 vol. 5(Issue 25) pp:19647-19651
Publication Date(Web):02 Feb 2015
DOI:10.1039/C4RA16506C
(1 − x)[0.93(K0.5Na0.5)NbO3–0.07LiNbO3]–xCaZrO3 (KNN–LN–xCZ) lead-free piezoelectric ceramics have been prepared by the conventional solid state reaction method and investigated to differentiate the effects of polymorphic phase transition. The crystal structure of the ceramics changed from orthorhombic to tetragonal at x ≥ 0.04, and then both the orthorhombic and tetragonal phases coexisted in the region of 0.04 < x < 0.08 composition, and the orthorhombic–tetragonal phase transition temperature was modified to around room temperature. Remarkably, piezoelectric and ferroelectric properties have been obtained for KNN–LN–xCZ ternary system with x = 0.04, in which the piezoelectric parameter of d*33 was 320 pm V−1 with Curie temperature Tc = 350 °C, strain level = 0.16% at 50 kV cm−1 and remnant polarization Pr = 27.2 μC cm−2.
Co-reporter:Wei Li, Peng Li, Huarong Zeng, Jigong Hao and Jiwei Zhai
RSC Advances 2015 vol. 5(Issue 8) pp:6181-6185
Publication Date(Web):04 Dec 2014
DOI:10.1039/C4RA13376E
The 0.755Bi0.5Na0.5TiO3–0.065BaTiO3–0.18SrTiO3/Ba0.98Ca0.02Ti0.96Sn0.04O3 (BNT–BT–ST/BCST) multilayered thin films, consisting of BNT–BT–ST layers and BCST layers, were prepared by using the sol–gel processing technique. The structure, leakage current, dielectric and piezoelectric properties of the multilayered thin films were investigated. Compositionally graded elemental profiles between individual BNT–BT–ST and BCST layers were achieved. The electric properties of the BNT–BT–ST/BCST multilayered thin films could be affected by the periodic layers. As a result, with an increase in periodic layers of the BNT–BT–ST/BCST multilayered thin films, the leakage current and dielectric loss were significantly reduced; moreover, the piezoelectric responses could be maintained at a high level (d33 = 130–150 pm V−1). This demonstrated the possibility to improve certain properties of the leakage current and dielectric loss for multilayered thin films, which could be exploited for functional devices that demand high quality.
Co-reporter:Peng Li, Jiwei Zhai, Huarong Zeng, Kunyu Zhao, Bo Shen, Haydn Chen
Ceramics International 2015 Volume 41(Issue 10) pp:12980-12987
Publication Date(Web):December 2015
DOI:10.1016/j.ceramint.2015.06.141
In this work, the high-quality 0.94(Bi0.5Na0.5)TiO3–0.06BaTiO3 (hereafter abbreviated as BNT–BT) lead-free piezoelectric thin films were synthesized by introducing LaNiO3 (hereafter abbreviated as LNO) seeding layers. The effects of LNO seeding layers on the crystal structure and electrical properties were systematically investigated. The X-ray diffraction patterns indicate that highly (100)-oriented BNT–BT films were prepared through utilizing LNO seeding layers. The maximum piezoelectric coefficient d33⁎ of ~100 pm/V, remanent polarization 2Pr of ~18 μC/cm2 and dielectric constant ɛr ~410 have been obtained in the highly (100)-oriented BNT–BT films. The observed tremendous enhancement of piezoresponse, ferroelectric and dielectric properties in LNO-seeded films can be attributed to the better crystallization quality, higher degree of (100)-preferred orientation and reduced leakage current density. These findings demonstrate that LNO-seeded BNT–BT thin films integrating with silicon substrates may provide a wide range of applications in high-performance MEMS devices.
Co-reporter:Peng Li, Wei Li, Huarong Zeng, Shaohui Liu, Wei Wang, Jiwei Zhai
Ceramics International 2015 Volume 41(Issue 3) pp:4479-4486
Publication Date(Web):April 2015
DOI:10.1016/j.ceramint.2014.11.140
Lead-free piezoelectric 0.9(0.8Bi0.5Na0.5TiO3–0.2Bi0.5K0.5TiO3)–0.1SrTiO3 thin films doped with x mol% La (abbreviated as BNT–BKT–ST–xLa) (x=0, 0.5, 1.0, 1.5) were prepared by a sol–gel method on Pt(1 1 1)/Ti/SiO2/Si substrates. The effects of La content on the microstructure, ferroelectric and piezoelectric properties were investigated systematically. The X-ray diffraction patterns indicated that all films had a single-phase perovskite structure. Meanwhile, we found that lanthanum content had great influence on the grain size and electrical properties. The thin film with a composition of BNT–BKT–ST–0.5La showed the optimal electrical properties with a remnant polarization, dielectric constant and effective piezoelectric constant of 10 μC/cm2, 560, and 83 pm/V, respectively. The results indicated that 0.5 mol% La-doped BNT–BKT–ST thin films would be of great interest for lead-free piezoelectric devices.
Co-reporter:Peng Li, Wei Li, Shaohui Liu, Yang Zhang, Jiwei Zhai, Haydn Chen
Ceramics International 2015 Volume 41(Supplement 1) pp:S344-S348
Publication Date(Web):July 2015
DOI:10.1016/j.ceramint.2015.03.177
The lead-free Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3–SrTiO3 (BNT–BKT–ST) and (La, Fe)-codoped Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3–SrTiO3 (BNT–BKT–ST–LaFe) thin films were deposited on Pt/Ti/SiO2/Si substrates by the sol–gel method. Both the BNT–BKT–ST and BNT–BKT–ST–LaFe thin films exhibit pseudo-cubic perovskite structure and uniform grain size. The leakage current density of BNT–BKT–ST–LaFe thin film at 400 kV/cm is reduced by approximately two orders of magnitude compared with BNT–BKT–ST thin film. Enhanced ferroelectric property is achieved in BNT–BKT–ST–LaFe film with a large remanent polarization of 13 μC/cm2. At the same time, the BNT–BKT–ST–LaFe film also exhibits a large dielectric constant of 420 and small dielectric loss of 0.055 at 100 kHz. These results indicate that the (La, Fe)-codoped BNT–BKT–ST thin film is a promising candidate in lead-free ferroelectric materials.
Co-reporter:Wei Li, Peng Li, Huarong Zeng, Jigong Hao, Jiwei Zhai
Ceramics International 2015 Volume 41(Supplement 1) pp:S356-S360
Publication Date(Web):July 2015
DOI:10.1016/j.ceramint.2015.03.178
0.755(Bi0.5Na0.5)TiO3–0.065BaTiO3–0.18SrTiO3 (BNT–BT–ST) thin films were deposited on the Pt(111)/Ti/SiO2/Si substrates with seed layer. Extremely enhanced electrical properties exhibited in the BNT–BT–ST film with seed layer, such as large dielectric constant (630) and piezoelectric coefficient d33 (140 pm/V) and low dielectric loss (0.032). The enhancement of electrical properties can be attributed to the seed layer, which offers nucleation site to reduce crystallization activation energy and facilitates polarization response. The seed layer also acts as a capacitive interface layer, which reduces the vacancy-type defects effectively.
Co-reporter:Shaohui Liu, Shuangxi Xue, Wenqin Zhang, Jiwei Zhai, Guohua Chen
Ceramics International 2015 Volume 41(Supplement 1) pp:S430-S434
Publication Date(Web):July 2015
DOI:10.1016/j.ceramint.2015.03.175
Flexible Poly(vinylidene fluoride) (PVDF) composites with high storage density have attracted considerable research interests in the past years. The dielectric and energy storage properties of PVDF composites are highly influenced by the crystalline phase. The effect of an quenched technique on the crystalline phase, dielectric constants and energy storage density in PVDF composites consisting of 2.5 vol% surface-modified Ba0.6Sr0.4TiO3 nanofibers (BST NF) by 3-aminopropyltriethoxysilane (APS) has been investigated. The results show that the untreated PVDF composites are dominated by the β-phase, while the quenched PVDF composites are primarily in the α-phase. The quenched PVDF composites containing of 2.5 vol% of APS modified BST NF exhibited energy density as high as 6.8 J/cm3 at 3800 kV/cm, which is more than 4.2 times larger than that of untreated PVDF composites. This work may provide a route for using the quenched technique to enhance the dielectric energy density in ceramic–polymer composites.
Co-reporter:Shuangxi Xue, Shaohui Liu, Wenqin Zhang, Bo Shen, Jiwei Zhai
Ceramics International 2015 Volume 41(Supplement 1) pp:S441-S446
Publication Date(Web):July 2015
DOI:10.1016/j.ceramint.2015.03.176
The (BaO, Na2O)–Nb2O5–SiO2 glass-ceramics with various amounts of La2O3 addition, were fabricated through melt casting followed by controlled crystallization. The effect of La2O3 addition on the phase transition, microstructure, and dielectric properties for (BaO, Na2O)–Nb2O5–SiO2 glass-ceramics was investigated. With the addition of La2O3, the dielectric constant and the breakdown strength for the glass-ceramics were drastically improved, which resulted in the improvement of the discharged property. The maximum energy-storage density of 8.4 J/cm3 was achieved in the niobate glass-ceramics with 0.5% La2O3 addition, indicating that the glass-ceramic with this composition is a promising dielectric material for high energy storage density capacitors.
Co-reporter:Zifang He, Ruirui Liu, Pengzhi Wu, Jiwei Zhai, Tianshu Lai, Sannian Song, Zhitang Song
Journal of Alloys and Compounds 2015 Volume 653() pp:334-337
Publication Date(Web):25 December 2015
DOI:10.1016/j.jallcom.2015.09.008
•Smaller volume shrinkage (2.21%) guarantees high reliability operation.•The crystallization speed of [Ge8Sb92(25 nm)/Ga30Sb70(25 nm)]1 film was about 11 ns.•The Ge8Sb92/Ga30Sb70 stacked thin films show better thermal stability than Ge2Sb2Te5.•The reversible transition speed of the cell is as short as 50 ns.Stacked Ge8Sb92/Ga30Sb70 films exhibited better thermal stability. Smaller volume change (2.21%) before and after phase change than Ge2Sb2Te5 (GST). Crystallization process of the [Ge8Sb92(25 nm)/Ga30Sb70(25 nm)]1 thin film was within 11 ns, which was measured by a picosecond laser pump-probe system. Reversible transition of the phase change memory cell based on the [Ge8Sb92(25 nm)/Ga30Sb70(25 nm) ]1 can be achieved by using an electrical pulse of as short as 50 ns.
Co-reporter:Wangfeng Bai, Feng Liu, Peng Li, Bo Shen, Jiwei Zhai, Haydn Chen
Journal of the European Ceramic Society 2015 Volume 35(Issue 13) pp:3457-3466
Publication Date(Web):November 2015
DOI:10.1016/j.jeurceramsoc.2015.05.001
The structure of end-member Bi(Ni0.5Ti0.5)O3 was calculated by first-principles method and solid solution of the (1 − x)BNT–xBi(Ni0.5Ti0.5)O3 ((1 − x)BNT–xBNiT) system was prepared using solid state reaction. Effect of BNiT addition to BNT ceramics on the phase structure, strain behavior, dielectric, ferroelectric, and piezoelectric properties was systematically investigated. The phase diagram was obtained and the relationship between the phase structure and electromechanical properties has been clarified. In comparison to other systems, results in this study indicated a relationship between the morphotropic phase boundary (MPB) composition and tolerance factor and the calculated tetragonality of the end-member Bi(Me′0.5Me″0.5)O3, and the t value corresponding to the formation of MPB located in a quite narrow range of 0.975–0.976 in the (1 − x)BNT–xBi(Me′0.5Me″0.5)O3 systems with low tolerance factor end-members. Thus, this work do not only supplement for BNT-based piezoceramics, but also provide a guideline to predict the approximate MPB region quickly for designing new lead-free piezoelectric ceramics.
Co-reporter:Wangfeng Bai, Junhua Xi, Jun Zhang, Bo Shen, Jiwei Zhai, Haixue Yan
Journal of the European Ceramic Society 2015 Volume 35(Issue 9) pp:2489-2499
Publication Date(Web):September 2015
DOI:10.1016/j.jeurceramsoc.2015.03.016
<0 0 l>-textured 0.83Na0.5Bi0.5TiO3–0.17Bi0.5K0.5TiO3 (BNT–BKT) ceramics with high degree of texturing (>80%) were synthesized by templated grain growth using different perovskite plate-like BaTiO3, SrTiO3 and NaNbO3 as template particles to develop lead-free piezoelectric materials with an excellent actuating performance. The effects of different template particles addition to BNT–BKT ceramics on the grain orientation, structure evolution, phase stability and macroscopic functional properties was systematically investigated. BaTiO3 template particles addition to form <0 0 l>-textured BNT–BKT–BT textured ceramics suppresses an electric-field-induced long-range ferroelectric order, giving rise to a high field-induced Smax/Emax of 710 pm/V under a relatively low driving field of 45 kV/cm compared with existing lead-free Bi-perovskite ceramics. In particular, temperature-dependent strain response reveals that <0 0 l>-textured BNT–BKT–5BT ceramics exhibit not only large Smax/Emax at a low driving field of 45 kV/cm at room temperature but also enhanced the temperature stability of Smax/Emax featured by large Smax/Emax of 517 pm/V at high temperature.
Co-reporter:Peng Li, Wei Li, Jiwei Zhai, Bo Shen, Huarong Zeng and Kunyu Zhao
RSC Advances 2015 vol. 5(Issue 77) pp:62713-62718
Publication Date(Web):14 Jul 2015
DOI:10.1039/C5RA10795D
In the present study, lead-free (1 − x)Bi0.5(Na0.8K0.2)0.5TiO3-xBiMnO3 (abbreviated as BNKT-xBMO, with x ranging from 0 to 0.025) thin films were deposited on Pt/Ti/SiO2/Si substrates by a sol–gel method, and the effects of BiMnO3 addition on the crystal structure and electrical properties were systematically investigated. The results show that with increasing BiMnO3 content the crystal structure undergoes a phase transition from a ferroelectric rhombohedral phase to rhombohedral-tetragonal coexisting phases to a relaxor pseudocubic phase. The superior ferroelectric, piezoelectric and dielectric properties were attained at x = 0.01 with remanent polarization 2Pr ∼ 14 μC cm−2, effective piezoelectric coefficient d*33 ∼ 116 pm V−1 and dielectric constant εr ∼ 270. The composition-dependent phase structure and optimal electrical properties indicated that the MPB-like behavior existed at around x = 0.01. Moreover, our study revealed that the end-member BiMnO3 modified BNKT thin films provided a lead-free alternative in ferroelectric random access memory (FRAM) and piezoelectric actuator application.
Co-reporter:Shaohui Liu, Shi Xiao, Shaomei Xiu, Bo Shen, Jiwei Zhai and Zhenlian An
RSC Advances 2015 vol. 5(Issue 51) pp:40692-40699
Publication Date(Web):28 Apr 2015
DOI:10.1039/C5RA05095B
We report nanocomposites with an increased dielectric constant, enhanced electric breakdown strength and high-energy density based on a surface-modified Ba0.6Sr0.4TiO3 nanofiber (BST NF) filled poly(vinylidene fluoride) polymer. To improve the dispersion stability of the fillers in the polymer matrices, surface modification of the dielectric fillers was obtained through functionalization of the BST NF by hydroxylation using H2O2 treatment and subsequent fluorination. The surface-fluorinated BST NF (F-BST NF) exhibit excellent dispersion in the PVDF polymer matrix and strong interfacial adhesion with the matrix, leading to excellent flexibility for the composites. The composites exhibit the optimum dielectric performance (i.e. high dielectric constant and high breakdown strength). With 2.5 vol% of F-BST NF, the extractable energy density of the F-BST NF/PVDF composites is 7.5 J cm−3, which is three times as high as that of a pure PVDF matrix, showing good potential for energy storage applications. Our strategy provides a simple but effective way to prepare high performance flexible dielectric composite capacitors with high storage density.
Co-reporter:Wangfeng Bai, Lingyu Li, Wei Wang, Bo Shen, Jiwei Zhai
Solid State Communications 2015 Volume 206() pp:22-25
Publication Date(Web):March 2015
DOI:10.1016/j.ssc.2015.01.004
•Phase diagram for the (Bi0.5Na0.5)TiO3–KNbO3–SrTiO3 ternary system has been constructed and analyzed based on macroscopic properties and structure analysis.•A very high electrostrictive strain (~0.148%) with a high electrostrictive coefficient Q11 of 0.0236 m4 C−2 is obtained for the 0.90BNT–0.08KN–0.02ST composition, which was entirely comparable to the well-known electrostrictive material Pb(Mg1/3Nb2/3 )O3.•The electrostrictive coefficient exhibited a highly temperature-insensitive behavior.In this work, phase diagram for the (Bi0.5Na0.5)TiO3–KNbO3–SrTiO3 ternary system has been constructed and analyzed based on macroscopic properties and structure analysis and pseudocubic (0.92−x)BNT–0.08KN–xST (0≤x≤0.07) ceramics have been fabricated and investigated. A morphotropic phase boundary between the ferroelectric rhombohedral and relaxor pseudocubic phases at around critical composition was proposed, resulting in large strain response. The polarization hysteresis loops, strain hysteresis loops and S–P2 curves demonstrate electrostrictive behavior of all studied samples. A very high electrostrictive strain (~0.148%) with a high electrostrictive coefficient Q11 of 0.0236 m4 C−2 is obtained for the 0.90BNT–0.08KN–0.02ST composition, which was entirely comparable to the well-known electrostrictive material Pb(Mg1/3Nb2/3 )O3 and attributed to the formation of relaxor pseudocubic phase developed by the SrTiO3 substitution. Meanwhile, the electrostrictive coefficient exhibited a highly temperature-insensitive behavior, indicating that the investigated system is suitable for high-precision positioning devices and solid-state actuators.
Co-reporter:Xihong Hao, Jiwei Zhai, Ling Bing Kong, Zhengkui Xu
Progress in Materials Science 2014 Volume 63() pp:1-57
Publication Date(Web):June 2014
DOI:10.1016/j.pmatsci.2014.01.002
Lead zirconate (PbZrO3 or PZ)-based antiferroelectric (AFE) materials, as a group of important electronic materials, have attracted increasing attention for their potential applications in high energy storage capacitors, micro-actuators, pyroelectric security sensors, cooling devices, and pulsed power generators and so on, because of their novel external electric field-induced phase switching behavior between AFE state and ferroelectric (FE) state. The performances of AFE materials are strongly dependent on the phase transformation process, which are mainly determined by the constitutions and the external field. For AFE thin/thick films, the electrical properties are also strongly dependent on their thickness, crystal orientation and the characteristics of electrode materials. Accordingly, various strategies have been employed to tailor the phase transformation behavior of AFE materials in order to improve their performances. Due to their relatively poor electrical strength (low breakdown fields), most PZ-based orthorhombic AFE ceramics are broken down before a critical switching field can be applied. As a consequence, the electric-field-induced transition between AFE and FE phase of only those AFE bulk ceramics, with compositions within tetragonal region near the AFE/FE morphotropic phase boundary (MPB), can be realized experimentally at room temperature. AFE materials with such compositions include (Pb,A)ZrO3 (A = Ba, Sr), (Pb1−3/2xLax)(Zr1−yTiy)O3 (PLZT x/(1−y)/y), (Pb0.97La0.02)(Zr,Sn,Ti)O3 (PLZST) and Pb0.99(Zr,Sn,Ti)0.98Nb0.02O3 (PNZST). As compared to bulk ceramics, AFE thin and thick films always display better electric-field endurance ability. Consequently, room temperature electric-field-induced AFE–FE phase transition could be observed in the AFE thin/thick films with orthorhombic structures. Moreover, AFE films are more easily integrated with silicon technologies. Therefore, AFE thin/thick films have been a subject of numerous researches. This review serves to summarize the recent progress of PZ-based AFE materials, focusing on the external field (electric field, hydrostatic pressure and temperature) dependences of the AFE–FE phase transition, with a specific attention to the performances of AFE films for various potential applications, such as high energy storage, electric field induced strains, pyroelectric effect and electrocaloric effect.
Co-reporter:Shaohui Liu, Shuangxi Xue, Wenqin Zhang, Jiwei Zhai and Guohua Chen
Journal of Materials Chemistry A 2014 vol. 2(Issue 42) pp:18040-18046
Publication Date(Web):10 Sep 2014
DOI:10.1039/C4TA04051A
Polymer composite flexible films with high dielectric constant are highly desirable in electronic and electrical industry. Higher loading of the ceramic fillers is usually needed in order to realize high dielectric constant. However, such composites exhibit low breakdown strength and poor mechanical and processing properties. In this work, by incorporating high aspect ratio surface-hydroxylated Ba0.6Sr0.4TiO3 nanotubes (BST NT) prepared via electrospinning into a polyvinylidene-fluoride (PVDF) matrix, PVDF nanocomposite flexible films with high dielectric constant have been successfully obtained. The nanocomposite containing 10 vol% BST NT-OH has a dielectric constant of 48.2 at 1 kHz, which is 6.1 times higher than that of the pure PVDF (7.9). The dielectric properties of the composites are closely related to the combined effects of the surface modification, large aspect ratio, high surface area and paraelectric polarization behavior of the BST NT.
Co-reporter:Liu Shaohui, Zhai Jiwei, Wang Jinwen, Xue Shuangxi, and Zhang Wenqin
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 3) pp:1533
Publication Date(Web):January 10, 2014
DOI:10.1021/am4042096
The ceramic–polymer nanocomposites consisting of Ba0.6Sr0.4TiO3 nanofibers (BST60 NF) with a large aspect ratio prepared via electrospinning and employing surface hydroxylated as fillers and poly(vinylidene fluoride) (PVDF) as matrix have been fabricated by a solution casting method. The nanocomposites exhibit enhanced permittivity, reduced loss tangents and improved breakdown electric field strength at a low volume fraction of hydroxylated BST60 NF. The energy density of the nanocomposites is significantly enhanced, and the maximal energy density of 6.4 J/cm3 is obtained in the composite material with 2.5 wt % hydroxylated BST60 NF, which is more than doubled as compared with the pure PVDF. Such significant enhancements result from combined effect of the large aspect ratio, the surface modification and the improved crystallinity of the nanocomposites induced by the hydroxylated BST60 NF. This work may provide a route for using the hydroxylated ceramic nanofibers to enhance the dielectric energy density in ceramic–polymer nanocomposites.Keywords: Ba0.6Sr0.4TiO3 nanofiber; energy density; nanocomposites; surface hydroxylation;
Co-reporter:Xiaoyi Feng, Ting Wen, Jiwei Zhai, Tianshu Lai, Changzhou Wang, Sannian Song, Zhitang Song
Applied Surface Science 2014 Volume 316() pp:286-291
Publication Date(Web):15 October 2014
DOI:10.1016/j.apsusc.2014.07.138
Highlights
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Films with different thickness ratios were deposited to prove the adjustable some properties.
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Optical reflectivity was involved to identify the phase change process and study the phase change speed.
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We manufactured PCRAM cells to measure the SET/RESET process.
Co-reporter:Wangfeng Bai, Lingyu Li, Wei Li, Bo Shen, Jiwei Zhai, Haydn Chen
Journal of Alloys and Compounds 2014 Volume 603() pp:149-157
Publication Date(Web):5 August 2014
DOI:10.1016/j.jallcom.2014.03.033
•Plate-like SrTiO3 particles with uniform microstructure were prepared.•The 〈0 0 l〉 textured BNT–BKT–ST ceramics were fabricated with high degree of orientation (f > 90%).•The relationship between the phase structure and the electrical properties was investigated.•Encouraging results of large strain of 0.38% with normalized strain Smax/Emax = 626 pm/V were obtained at critical composition.•The textured ceramics exhibited large electrostrictive coefficient Q11 of 0.023 m4 C−2 and superior temperature stability.In this work, 〈0 0 l〉 textured lead-free piezoelectric (1−x)(0.83 Bi0.5Na0.5TiO3–0.17Bi0.5K0.5TiO3)–xSrTiO3 (BNT–BKT–xST) ceramics were fabricated by template grain growth in combination with tape casting using plate-like SrTiO3 as a template. The effect of ST template on the grain orientation, strain behavior, dielectric, ferroelectric, pyroelectric and piezoelectric properties was systematically investigated in order to search the lead-free piezoelectric materials with an excellent actuating performance. The templated growth of 〈0 0 l〉 oriented grains on the ST template resulted in textured ceramics with brick wall microstructures and significantly high 〈0 0 l〉 texture degree corresponding to >90% Lotgering factor at 9–15 mol% ST template. Textured ceramics showed excellent strain properties as compared to the random counterparts and encouraging results of large strain of 0.38% with normalized strain Smax/Emax = 626 pm/V for the textured critical composition with 15 mol% ST template were obtained at room temperature. Furthermore, the textured ceramics with 27 mol% ST template exhibited large electrostrictive coefficient Q11 of 0.023 m4 C−2 and superior temperature stability compared to the random counterparts, which are very promising and makes them tremendous potential for the environmental-friendly solid-state actuator applications.
Co-reporter:Shuangxi Xue, Shaohui Liu, Wenqin Zhang, Jinwen Wang, Linjiang Tang, Bo Shen, Jiwei Zhai
Journal of Alloys and Compounds 2014 Volume 617() pp:418-422
Publication Date(Web):25 December 2014
DOI:10.1016/j.jallcom.2014.08.006
•High energy density and high charge-discharge efficiency.•The correlation between the BDS and the Ea was studied.•The discharge behaviors of the BNN based glass-ceramics were evaluated.A series of niobate glass ceramics with varying glass content have been prepared via controlled-crystallization route, and the dielectric properties, the breakdown characteristics and charge–discharge behaviors have been investigated. The correlation between the dielectric breakdown performance and the activation energy was studied by the measurements of the dielectric breakdown strength and impedance spectroscopy. The charge–discharge efficiency was investigated using a charge–discharge system with high-speed capacitor discharge circuit device. It was found that the dielectric breakdown strength and the discharge efficiency strongly depend on the interface polarization based on the results of complex impedance analysis. With the increase of the glass content, the breakdown strength (BDS) and the charge–discharge efficiency show a clear increasing trend, when the content of glass was 60%, the typical G60 sample shows a high BDS of 1300 kV/cm and a high charge–discharge efficiency of 92.5%.
Co-reporter:Yifeng Hu, Xiaoyi Feng, Jiwei Zhai, Ting Wen, Tianshu Lai, Sannian Song, Zhitang Song
Scripta Materialia 2014 Volume 93() pp:4-7
Publication Date(Web):15 December 2014
DOI:10.1016/j.scriptamat.2014.08.009
The amorphous-to-crystalline transitions of superlattice-like Ge8Sb92/Ge thin films were investigated through in situ film resistance measurement. X-ray reflectivity was used to measure the density change before and after phase change. The superlattice-like structure of the thin films was confirmed by using transmission electron microscopy. A picosecond laser pump–probe system was used to study the phase change speed. Phase change memory cells based on the SLL [Ge8Sb92(4 nm)/Ge(3 nm)]7 thin films were fabricated to test and verify the switching speed and operation consumption.
Co-reporter:Wei Li, Huarong Zeng, Kunyu Zhao, Jigong Hao, Jiwei Zhai
Ceramics International 2014 Volume 40(Issue 6) pp:7947-7951
Publication Date(Web):July 2014
DOI:10.1016/j.ceramint.2013.12.143
Lead free (1−x)(0.8Bi0.5Na0.5Ti0.5O3–0.2Bi0.5K0.5TiO3)–xBiZn0.5Ti0.5O3 (x=0–0.06) (BNT–BKT–BZT) thin films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by a sol–gel processing technique. The effects of BZT content on the structural, dielectric, ferroelectric and piezoelectric properties of the BNT–BKT–BZT thin films were investigated systematically. The BNT–BKT–BZT thin films undergo a transition from ferroelectric to relaxor phase with increasing temperature. The phase transition temperature decreases with the increase of BZT content. The BNT–BKT–BZT thin film with x=0.04 exhibits the best ferroelectric properties (Pmax=40 µC/cm2 and Pr=10 µC/cm2), largest dielectric constant (ε=560) and piezoelectric constant (d33=40 pm/V). This finding demonstrates that the BNT–BKT–BZT thin film has an excellent potential for demanding high piezoelectric properties in lead free films.
Co-reporter:Shaohui Liu and Jiwei Zhai
RSC Advances 2014 vol. 4(Issue 77) pp:40973-40979
Publication Date(Web):11 Aug 2014
DOI:10.1039/C4RA04369C
Compared to spherical ceramic fillers, ceramic fillers with large aspect ratios can increase the dielectric constant of nanocomposites at a much lower concentrations because their large dipole moments, and their smaller specific surface can help to reduce the surface energy and thus prevent the nanofillers from agglomerating in the polymer matrix. Therefore, high energy storage capability of the nanocomposite is obtained using surface-modified Ba0.6Sr0.4TiO3 nanofibers with a large aspect ratio (BST NF) by 3-aminopropyltriethoxysilane (APS) filling in a poly(vinylidene fluoride) polymer (PVDF) matrix. The nanocomposites exhibit enhanced dielectric constant and reduced loss tangents at a low volume fraction of surface-modified BST NF. The maximal energy density in the nanocomposite with 2.5 vol% BST NF-APS is about 6.8 J cm−3 at 3800 kV cm−1, about 143% higher than that of the PVDF of 2.8 J cm−3 at 4000 kV cm−1. The enhanced energy storage density could be attributed to the combined effects of surface modification by the APS, large aspect ratio and paraelectric polarization behavior of the BST NF. This work may provide a novel route for using the small loading of surface-modified paraelectric ceramic fillers with large aspect ratios for enhanced energy-storage density in polymer composites.
Co-reporter:Yanlong Bian, Jiwei Zhai
Journal of Physics and Chemistry of Solids 2014 Volume 75(Issue 6) pp:759-764
Publication Date(Web):June 2014
DOI:10.1016/j.jpcs.2014.02.002
•Dielectric properties of the Ba0.6Sr0.4TiO3/MgTiO3 (BST/MT) composite films were investigated.•Thickness of MT layer affects the dielectric properties of thin films.•Composite films show the highest figure of merit (FOM) when the MT layer has a thickness of 15 nm.•The improvement in dielectric properties is due to the MT insertion.The dielectric properties of Ba0.6Sr0.4TiO3 (BST)/MgTiO3 (MT) composite thin films deposited on Pt(1 1 1)/Ti/SiO2/Si(1 0 0) substrates by the sol–gel method were investigated. The X-ray pattern analysis indicates that the thin films exhibit good crystalline quality with perovskite phase and that insertion of MT layer does not obviously affect the phase structure of BST thin films. The characterization of dielectric properties demonstrates that configuration of BST/MT/BST thin films is an effective approach to obtain low dielectric loss and dielectric tunability of BST thin films. At room temperature, the tunability of pure BST60 films and BST/MT (15 nm)/BST composite thin films is 47% and 36%, respectively, at the frequency of 1 MHz with an applied electric field of 400 kV/cm. For BST/MT/BST composite thin films, considerable reduction in the dielectric loss values is observed, which renders them attractive for tunable microwave device applications.
Co-reporter:Fang Fu;Zhengkui Xu;Bo Shen;Xi Yao
Bulletin of Materials Science 2014 Volume 37( Issue 4) pp:779-787
Publication Date(Web):2014 June
DOI:10.1007/s12034-014-0006-5
Textured BaTiO3 (BT) ceramics were fabricated by templated grain growth method. Effects of sintering conditions on the grain growth process of textured-BT ceramics were investigated. Orientation degree increased initially and then decreased with increasing soaking time. The ceramics were composed of equiaxed matrix grains and brick-like template particles. The brick-like particles aligned parallel to the casting direction by observing from SEM images. A (h00)-preferred orientation was confirmed by SAED and XRD patterns. Mechanism of grain growth in textured-BT ceramics was studied. Both consumption of matrix by templates and grain growth of templates determined the orientation degree of ceramics. The kinetic mechanism for grain orientation was also discussed by the simplified phenomenological kinetic equation. The average activation energies were 364 kJ/mol for matrix grain and 918 kJ/mol for template particle, respectively. Finally, a dense ceramic with 85% grain orientation was obtained after sintering at 1400 °C for 2 h.
Co-reporter:Fang Fu;Bo Shen;Zhengkui Xu
Journal of Electroceramics 2014 Volume 33( Issue 3-4) pp:208-213
Publication Date(Web):2014 December
DOI:10.1007/s10832-014-9952-y
(h00)-textured BaTiO3 thick film was fabricated on Pt substrate by screen printing method. Effects of template content on grain orientation and electric properties of the thick film were investigated. Grain orientation degree of thick film was optimized to 81 % with 20 % template content. Saturate polarization and coercive field of the textured thick film were 7.5μC/cm2 and 2.9 kV/cm, respectively. A diffusion behavior was observed by the temperature dependence of dielectric constant of BaTiO3 thick films. Piezoelectric properties of the thick film were characterized by relationship of unipolar strain and applied electric field. Piezoelectric constant d33* of grain orientation thick film was 136 pm/V, which was higher than that of non-textured film (d33* = 92 pm/V).
Co-reporter:Yanlong Bian
Journal of Sol-Gel Science and Technology 2014 Volume 69( Issue 1) pp:40-46
Publication Date(Web):2014 January
DOI:10.1007/s10971-013-3182-7
The Ba0.6Sr0.4TiO3 (BST60) thin films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by a sol–gel method. The thickness of CeO2, serving as a buffer layer, was varied from 0 to 75 nm, in order to optimize the dielectric tunable property. X-ray patterns analysis indicates that all the thin films exhibit good crystalline quality with a pure perovskite phase and insertion of the CeO2 buffer layer does not change the crystal structure of BST60. Dielectric properties of the thin films were investigated as a function of both temperature and direct current electric field. The results show that dielectric constant and loss are modified by insertion of the CeO2 buffer layer. The BST60 thin films with 25 nm thickness CeO2 buffer layer have the highest figure of merit, low dielectric loss, and suitable dielectric constant, which render them attractive for the tunable microwave device applications.
Co-reporter:Yifeng Hu, Simian Li, Tianshu Lai, Sannian Song, Zhitang Song, Jiwei Zhai
Journal of Alloys and Compounds 2013 Volume 581() pp:515-518
Publication Date(Web):25 December 2013
DOI:10.1016/j.jallcom.2013.07.133
•Al-doped Sn2Se3 thin films were investigated for phase-change memory applications.•The thermal stability of Sn2Se3 thin films were improved by Al doping.•A fast transition speed was observed in Al-doped Sn2Se3 thin films by the picosecond laser pulses.•A lower power consumption of PCM cells could be achieved by Al doping.Phase change behavior in Al-doped Sn2Se3 thin films were investigated by utilizing in situ resistance measurements. It is found that the crystallization temperature and resistance increase with increasing of Al content. AFM images demonstrated Al-doping reduced the surface roughness and inhibited the crystallization of Sn2Se3 thin films. A smaller density change before and after phase change for Al0.023(Sn2Se3)0.977 thin films was obtained from X-ray reflectivity. The phase transition speed between the amorphous and crystalline state was investigated by the picosecond laser pulses. The obtained values of Avrami indexes indicate that a one dimensional growth-dominated mechanism is responsible for the set transition of Al0.023(Sn2Se3)0.977 thin film. Phase transition is observed at relatively lower power, compared with a device using Ge2Sb2Te5 film.
Co-reporter:Qigang Zhou, Jiwei Zhai
Applied Surface Science 2013 Volume 284() pp:644-650
Publication Date(Web):1 November 2013
DOI:10.1016/j.apsusc.2013.07.148
Highlights
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High temperature conducting ZrNx films were deposited on silicon-based substrates as bottom electrodes for resistive random access memory (RRAM) application in Pt/HfOx/ZrNx sandwich structure.
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In contrast to the memory cells in Pt/HfOx/Pt structure, the Pt/HfOx/ZrNx cells show a robust endurance, low and stable operation parameters, large memory window and good retention ability.
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The interface Zirconium oxynitride between the dielectric HfOx film and the ZrNx bottom electrode play key roles in the RS performance improvement.
Co-reporter:Huanbei Chen, Bo Shen, Jinbao Xu, Jiwei Zhai
Journal of Alloys and Compounds 2013 Volume 551() pp:92-97
Publication Date(Web):25 February 2013
DOI:10.1016/j.jallcom.2012.09.149
Due to the poor insulating property of the pure bismuth titanate Bi4Ti3O12 (BIT) ceramic, it is very difficult to obtain the piezoelectric properties. This study focuses on the effect of the grain size on the electric properties and thermal stability of BIT ceramics. The BIT ceramic with different grain sizes from 4.2 μm to 0.28 μm were prepared by three sintering methods: normal sintering, two-step sintering and hot pressing sintering. Result shows that the problem of large leakage current of BIT ceramics can be solved by reducing grain size. The piezoelectric properties of BIT ceramics have a strong dependence on the grain size since two factors of internal stress and poling electric field strength both influences the degree of ferroelectric domain switching. The thermal stability is decreased with decreasing of the grain size since internal stresses provide an additional driving force that assists the thermal depolarization.Highlights► The Bi4Ti3O12 ceramic with grain sizes from 4.2 μm to 0.28 μm were prepared. ► Large leakage current of it can be solved by reducing grain size. ► The piezoelectric properties of it have a strong dependence on the grain size. ► The thermal stability is decreased with decreasing of the grain size.
Co-reporter:Yifeng Hu, Mingcheng Sun, Sannian Song, Zhitang Song, Jiwei Zhai
Journal of Alloys and Compounds 2013 Volume 551() pp:551-555
Publication Date(Web):25 February 2013
DOI:10.1016/j.jallcom.2012.11.032
The amorphous-to-crystalline transitions of oxygen-doped Sb4Te (STO) films are investigated by in situ film resistance measurements. The crystalline temperature and resistance of the oxygen-doped films increase. The analysis of X-ray diffractomer (XRD) and X-ray photoelectron spectroscopy (XPS) indicate that the films with doping of a small amount of oxygen atoms can refine the grain size and form oxide, improving the resistance and thermal stability of phase change films. Excessive oxygen in Sb4Te will make Te separate, resulting in deteriorating the stability. As a result, STO2 film has the relatively high activation energy for crystallization. The 10-year lifetime is raised from 29 °C of undoped Sb4Te film to 102 °C of STO3 film. Phase transition from amorphous state to crystalline state is observed at relatively lower power, compared with a device using Ge2Sb2Te5 film.Highlights► O-doped Sb4Te phase-change films were reported. ► The amorphous-to-crystalline transitions of O-doped Sb4Te films were studied. ► By doping oxygen, the stability of Sb4Te films is improved greatly. ► The resistance of the Sb4Te films increases by doping oxygen.
Co-reporter:Linjiang Tang, Jiwei Zhai, Haijun Zhang, Xi Yao
Journal of Alloys and Compounds 2013 Volume 551() pp:556-561
Publication Date(Web):25 February 2013
DOI:10.1016/j.jallcom.2012.10.189
(1 − x)Ba0.5Sr0.5TiO3–xAMoO4 (A = Ba, Sr) ceramics with x = 5, 10, 20 and 30 wt% were prepared by traditional solid-state reaction method. Two crystalline phases, a cubic perovskite structure Ba0.5Sr0.5TiO3 (BST) and a tetragonal scheelite structure AMoO4 were observed by XRD analysis. The microwave dielectric properties of Ba0.5Sr0.5TiO3–AMoO4 composite ceramics were investigated systematically. With increasing content of AMoO4 from 5% to 30%, the dielectric anomalous peaks of ferroelectric–paraelectric phase transition for the composite ceramics are suppressed and broadened. The results show that the composite ceramics exhibited promising microwave properties. Especially, in the (1 − x)Ba0.5Sr0.5TiO3–xSrMoO4 system the dielectric constant can be adjusted in the range from 1200 to 132, while maintaining tunability from 38.3% to 6.4% (60 kV/cm) and Q values more than 259 in the gigahertz frequency region. So (1 − x)Ba0.5Sr0.5TiO3–xSrMoO4 composite ceramic is a promising candidate for electrically tunable microwave device applications.Highlights► (1 − x)Ba0.5Sr0.5TiO3–xAMoO4 (A = Ba, Sr) were prepared and their property were investigated. ► A new kind of composite with high tunability, low dielectric constant. ► Binary composite structures have the greatly enhanced dielectric properties. ► The samples of (1 − x)Ba0.5Sr0.5TiO3–xAMoO4 has the level of Q value (⩾259).
Co-reporter:Bo Shen, Qiwei Zhang, Jiwei Zhai, Zhengkui Xu
Ceramics International 2013 Volume 39(Supplement 1) pp:S9-S13
Publication Date(Web):May 2013
DOI:10.1016/j.ceramint.2012.10.026
Abstract
Barium zirconate titanate Ba(ZrxTi1−x)O3 (BZT) ceramics have been fabricated by conventional solid state route. The dielectric properties and ferroelectric relaxor behavior were investigated as a function of Zr content and DC bias field. It was found that the relaxor behavior of BZT is enhanced with the increase in Zr content. The temperature of maximum dielectric peak (Tm) of BZT ceramic is greatly increased with DC bias field (E) up to a certain threshold field Et, below which Tm starts to increase gradually. This behavior could be associated with the size of domain. The relationship between temperature and dielectric tunability is also discussed in details.
Co-reporter:Wangfeng Bai, Jigong Hao, Fang Fu, Wei Li, Bo Shen, Jiwei Zhai
Materials Letters 2013 Volume 97() pp:137-140
Publication Date(Web):15 April 2013
DOI:10.1016/j.matlet.2013.01.088
<00l> textured 0.72(Bi0.5Na0.5)TiO3–0.28SrTiO3 ()lead-free piezoelectric ceramic was fabricated by template grain growth using plate-like SrTiO3 as a template. The templated growth of <00 > oriented BNT–ST grains on the ST template resulted in textured ceramics with brick wall microstructures and a high degree of orientation of 82%. Relationships between microstructure and electric properties of the ceramics with different amount of template contents were investigated. The textured ceramics showed enhanced electric properties compared with the random counterparts and exhibited excellent piezoelectric performance with strain level of 0.39% at 70 kV/cm and normalized strain d33⁎ (Smax/Emax) of 557 pm/V, revealing that the textured ceramics have tremendous potential for possible actuator applications.Highlights► Plate-like SrTiO3 particles with uniform microstructure were prepared. ► <00l> textured BNT–ST ceramics were fabricated with high degree of orientation (f ∼82%). ► <00l> textured BNT–ST ceramics were reported and fabricated firstly by TGG using anisotropically shaped SrTiO3 templates, which is unique in this research area. ► High piezoelectric coefficient was achieved in textured BNT–ST ceramics.
Co-reporter:Qiwei Zhang, Jiwei Zhai, Bo Shen, Haijun Zhang, Xi Yao
Materials Research Bulletin 2013 48(3) pp: 973-977
Publication Date(Web):
DOI:10.1016/j.materresbull.2012.11.085
Co-reporter:Hui Wang;Yanlong Bian;Bo Shen
Journal of Electronic Materials 2013 Volume 42( Issue 6) pp:988-992
Publication Date(Web):2013 June
DOI:10.1007/s11664-013-2489-z
The microwave properties of barium strontium titanate (Ba0.6Sr0.4TiO3) thin films grown on (100) LaAlO3 (LAO) and (100) MgO single-crystal substrates through the sol–gel technique were investigated. The interdigital capacitor (IDC) technique was used to measure the nonlinear dielectric properties in the frequency range from 1 GHz to 10 GHz. The results show that the Curie temperature, capacitance, and tunability of the films are strongly dependent upon the substrate. The film fabricated on the LaAlO3 substrate has a higher tunability of 16.77% than that grown on the MgO substrate (∼8.38%), measured at 10 GHz with an applied voltage of 35 V. The loss tangent is a linear function of the frequency in the microwave range, and the film grown on the MgO substrate has a lower loss tangent than that grown on the LAO substrate. This work reveals the great potential of Ba0.6Sr0.4TiO3 (BST) films for application in tunable microwave devices.
Co-reporter:Yanlong Bian;Hui Wang
Journal of Electronic Materials 2013 Volume 42( Issue 10) pp:2926-2932
Publication Date(Web):2013 October
DOI:10.1007/s11664-013-2673-1
The dielectric and microwave properties of Ba0.6Sr0.4TiO3 (BST60) thin films with a MgO buffer layer deposited on Al2O3 substrates were investigated. Insertion of the MgO buffer layer is demonstrated to be an effective approach to fabricate low-dielectric-loss BST thin films. x-Ray pattern analysis indicates that the thin films exhibit good crystalline quality with a pure perovskite phase and that insertion of the MgO buffer layer does not change the crystal structure of BST. The nonlinear dielectric properties of the BST films were measured by using an interdigital capacitor (IDC). At room temperature, the tunability of the BST films with a MgO buffer layer was 24.1% at a frequency of 1 MHz with an applied electric field of 80 kV/cm. The dielectric loss of the BST thin films is only 0.005 to 0.007 in the frequency range from 20 Hz to 2 MHz, the same as for BST films prepared on single-crystal MgO substrates. The microwave dielectric properties of the BST thin films were also measured by a vector network analyzer from 50 MHz to 10 GHz.
Co-reporter:Linjiang Tang;Jinwen Wang
Journal of Electronic Materials 2013 Volume 42( Issue 8) pp:2542-2548
Publication Date(Web):2013 August
DOI:10.1007/s11664-013-2621-0
A sintering-aid system using melting of B-Li glass for barium strontium titanate (BST)-based compositions to be used in low-temperature cofired ceramic (LTCC) layers is introduced. The effects of the sintering aid on the microstructure, dielectric properties, and application in LTCC were investigated. The composition Ba0.5Sr0.5TiO3-SrMoO4 with 3 wt.% B-Li glass sintered at 950°C exhibits optimized dielectric properties, including low dielectric constant (368), low dielectric loss (0.007), and moderate tunability (13%, 60 kV/cm) at 10 kHz. At 1.44 GHz, it possesses a dielectric constant of 218 and Q value of 230. LTCC multilayer ceramic capacitors fabricated by the tape-casting process have steady relative tunability of 12% at 300 V, suggesting that BST50-SrMoO4-B-Li glass composite ceramic is a promising candidate for electrically tunable LTCC microwave device applications.
Co-reporter:Huanbei Chen;Bo Shen;Jinbao Xu
Journal of Electroceramics 2013 Volume 30( Issue 3) pp:133-138
Publication Date(Web):2013 May
DOI:10.1007/s10832-012-9774-8
Calcium bismuth niobate CaBi2Nb2O9 (CBN) ceramic is a promising candidate for high-temperature piezoelectric applications due to its high Curie temperature. However, the extremely low piezoelectric properties hinder its application. A combination method with element doping and texturing was used to improve the electric properties of CBN ceramic. First of all, the Mn element was chosen to be doped to improve the piezoelectric and resistance properties of CBN ceramic. Then, an optimal composition was subsequently textured by templated grain growth (TGG) method to further improve the piezoelectric properties. The piezoelectric properties, Curie temperature (Tc), and resistivity of textured Ca0.95Mn0.05Bi2Nb2O9 ceramics (d33 = 21, kp = 10.9 %, Tc = 942 °C, ρ = 2.1 × 105Ω·cm at 600 °C) were improved obviously compared to pure random CBN ceramics (d33 = 6, kp = 4.6 %, Tc = 930 °C, ρ = 0.6 × 105Ω · cm at 600 °C). Furthermore, it has excellent resistance to thermal depoling and keep about 5.7 % kp until the temperature up to 600 °C. This combination method makes the textured Ca0.95Mn0.05Bi2Nb2O9 ceramics to be a promising candidate for high-temperature piezoelectric applications.
Co-reporter:Wei Li;Jigong Hao;Wangfeng Bai
Journal of Sol-Gel Science and Technology 2013 Volume 66( Issue 2) pp:220-224
Publication Date(Web):2013 May
DOI:10.1007/s10971-013-2996-7
Lead free Ba0.98Ca0.02Ti0.96Sn0.04O3 (BCST) thin films with (110), (111) and (001) orientations were processed via chemical solution deposition, and effects of orientation on the dielectric and piezoelectric properties were investigated in some aspects. The (110) orientated BCST thin films exhibit highest Curie temperature (Tc of 85 °C) and lowest dielectric loss (tan δ of 0.02). While, the (111) orientated BCST thin films exhibit highest dielectric tunability (74 %) and largest piezoelectric coefficient (d33 of 78 pm/V), which indicate that it is a promising lead-free replacement for lead-based applications. The anisotropic dielectric and piezoelectric properties in the three kinds of oriented BCST films has been attributed to the difference of structure, in-plane stress and polarization rotation in orientation engineered BCST films. This work clearly reveals the dielectric and piezoelectric properties of BCST films exhibit a strong sensitivity to orientation.
Co-reporter:Fang Fu, Bo Shen, Jiwei Zhai, Zhengkui Xu, Xi Yao
Ceramics International 2012 Volume 38(Supplement 1) pp:S287-S290
Publication Date(Web):January 2012
DOI:10.1016/j.ceramint.2011.04.103
Textured K0.5Na0.5NbO3 thick film was prepared by the reactive templated grain growth method. The effects of Mn2+ doping on the phase structure, microstructure and electrical properties of the K0.5Na0.5NbO3 textured thick film were investigated. The grain orientation degree decreased with increasing Mn2+ and reduced to 50% for the thick film with 5 mol% Mn2+. The addition of Mn2+ improved the microstructure of the thick film. The electric properties of the thick film were also enhanced because of the high densification, the vacancy compensation effect and the acceptor doping effects of Mn2+. The K0.5Na0.5NbO3 thick film with 2 mol% Mn2+ doping possessed the optimum properties: Pr = 3.05 μC/cm2, Ec = 4.79 kV/cm, J = 4.6 × 10−6A/cm2 (at 25 kV/cm) and d33*=124 pm/V.
Co-reporter:Wei Li, Jigong Hao, Wangfeng Bai, Zhijun Xu, Ruiqing Chu, Jiwei Zhai
Journal of Alloys and Compounds 2012 Volume 531() pp:46-49
Publication Date(Web):5 August 2012
DOI:10.1016/j.jallcom.2012.03.110
Lead-free (Ba0.99Ca0.01)(Ti0.98Zr0.02)O3 + x mol% (x = 0–0.8) Yttrium ceramics (BCZT-Y) were prepared using the solid-state reaction technique. High piezoelectric coefficient of d33 = 360 pC/N and planar electromechanical coupling factor of kp = 42% were obtained at x = 0.2. Furthermore, greatly enhanced temperature stabilities of the piezoelectric properties were obtained in the temperature range from 20 to 100 °C, in which the BCZT-Y ceramics exhibited pure tetragonal phase. With the increase of Yttrium content, the orthorhombic–tetragonal phase transition shifted toward low temperature, while Curie temperature (TC) maintained at about 120 °C. The results indicate that the BCZT-Y ceramics are promising lead-free materials for practical applications.Highlights► Enhanced temperature stability was obtained in the range from 20 and 100 °C. ► TO–T shifted toward low temperature and Tc maintained 120 °C with the increase of Y. ► High d33 = 360 pC/N and kp = 42% were obtained for the sample of BCZT-Y2.
Co-reporter:Wangfeng Bai, Bo Shen, Fang Fu, Jiwei Zhai
Materials Letters 2012 Volume 83() pp:20-22
Publication Date(Web):15 September 2012
DOI:10.1016/j.matlet.2012.05.114
The (001) textured (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT) thick films were fabricated via screen printing using anisotropically shaped BaTiO3 templates on platinum substrate. The dielectric, ferroelectric, and piezoelectric properties of the random and textured BCZT thick films have been investigated. The orientation degree (Lotgering's factor) of 81% calculated from X-ray diffraction patterns was obtained. The Curie temperature of the textured BCZT thick film shifted to a high temperature in comparison with the random BCZT thick film. The textured BCZT thick film exhibited excellent electric properties with the piezoelectric constant d33⁎ = 427 pm/V and remnant polarization Pr = 15.8 μC/cm2 sintered at 1300 °C for 4 h with 81% of Lotgering's factor.Highlights► Plate-like BaTiO3 particles with uniform microstructure were prepared. ► The (001) textured BCZT thick films were fabricated with a high degree of orientation. ► The (001) textured BCZT thick films were fabricated firstly by screen printing. ► The (001) textured BCZT thick films were fabricated using BaTiO3 templates. ► High piezoelectric coefficient was achieved in textured BCZT thick film.
Co-reporter:Huanbei Chen, Bo Shen, Jinbao Xu, Jiwei Zhai
Materials Research Bulletin 2012 47(9) pp: 2530-2534
Publication Date(Web):
DOI:10.1016/j.materresbull.2012.05.009
Co-reporter:Fang Fu;Zhengkui Xu;Wangfeng Bai
Journal of Electronic Materials 2012 Volume 41( Issue 11) pp:3077-3081
Publication Date(Web):2012 November
DOI:10.1007/s11664-012-2197-0
Lead-free (KNa)0.44Li0.06Nb0.84Sb0.06Ta0.1O3 textured thick films with 25 μm thickness were fabricated by the reactive templated grain growth method. The influence of LiSbO3 substitution on the degree of grain orientation was investigated. The addition of LiSbO3 improved the dielectric properties of the K0.5Na0.5NbO3 potassium sodium niobate (KNN) textured thick films. Leakage current behavior of the thick film was also reduced due to the LiSbO3 doping, which is explicable based on the space-charge-limited current mechanism. It was also found that the problem of interface effect was alleviated due to the presence of LiSbO3. Piezoelectric properties of thick film were improved dramatically owing to the co-effect of texturing and LiSbO3 doping, with d33* being sharply increased from 38 pm/V to 173 pm/V.
Co-reporter:Haitao Jiang;Mingwei Zhang;Xi Yao
Journal of Materials Science 2012 Volume 47( Issue 6) pp:2617-2623
Publication Date(Web):2012 March
DOI:10.1007/s10853-011-6086-3
The (1−x) Ba0.40Sr0.60TiO3 (BST)−xZr0.80Sn0.20TiO4 (ZST) composite ceramics with x = 10, 20, 30, and 40 wt% were fabricated by conventional solid-state reaction method. With increasing of ZST content, the dielectric constant of composite ceramics was decreased and dielectric loss increases. The effect of ZnO addition to 70 wt% BST–30 wt% ZST composition on the microstructure and dielectric properties was investigated. The improvements in dielectric constant, dielectric loss, and microwave dielectric properties of composite ceramics can be achieved by ZnO addition. The sample with 98 wt% (70 wt% BST–30 wt% ZST)–2 wt%ZnO composition exhibits promising dielectric properties, with dielectric constant, loss tangent and tunability at 4 kV/mm, of 125, 0.0016 and 12%, at 10 kHz and room temperature. At ~2 GHz, it possesses a dielectric constant of 101 and a Q factor of 187, which makes it a good candidate for tunable microwave device applications.
Co-reporter:Fang Fu, Bo Shen, Jiwei Zhai, Zhengkui Xu, Xi Yao
Journal of Alloys and Compounds 2011 Volume 509(Issue 25) pp:7130-7133
Publication Date(Web):23 June 2011
DOI:10.1016/j.jallcom.2011.04.029
Lithium doped K0.5Na0.5NbO3 (abbreviated as KNN–xL, with x = 0.02, 0.04, 0.06, 0.08) thick films with a thickness of about 20 μm were prepared by a tape casting process. The presence of Li ions promoted the microstructure of these thick films. Coercive fields (Ec) of the thick films decreased with the addition of Li ions. Two phase transition temperatures, corresponding to TO–T and TC, were observed in the KNN–xL thick films. The sample with x = 0.06 exhibited an optimized value of d33 (91.6 pm/V), which was attributed to the formation of a morphotropic phase boundary.Highlights► Li doped KNN thick films were prepared by a tape casting process. ► The coercive fields decreased with the addition of Li ions. ► The thick film with 6 mol% Li exhibited an optimized value of d33 which was 92 pm/V.
Co-reporter:Changzhou Wang, Jiwei Zhai, Suyuan Bai, Bo Shen
Applied Surface Science 2011 Volume 257(Issue 14) pp:6296-6299
Publication Date(Web):1 May 2011
DOI:10.1016/j.apsusc.2011.02.070
Abstract
The reliability characteristics and thermal conductivity of Ga30Sb70/Sb80Te20 nanocomposite multilayer films were investigated by isothermal resistance and transient thermoreflectance (TTR) measurements, respectively. The crystallization temperature and activation energy for the crystallization can be modulated by varying the layer thickness of Ga30Sb70. A data retention time of ten years of the amorphous state [Ga30Sb70 (3 nm)/Sb80Te20 (5 nm)]13, [Ga30Sb70 (5 nm)/Sb80Te20 (5 nm)]10, and [Ga30Sb70 (10 nm)/Sb80Te20 (5 nm)]7 was estimated when ambient temperature is 137, 163, and 178 °C, respectively. Ga30Sb70/Sb80Te20 nanocomposite multilayer films were found to have lower thermal conductivity in both the amorphous and crystalline state compared to Ge2Sb2Te5 film, which will promise lower programming power in the phase-change random access memory.
Co-reporter:L.N. Gao, J.W. Zhai, X. Yao
Applied Surface Science 2011 Volume 257(Issue 9) pp:3836-3839
Publication Date(Web):15 February 2011
DOI:10.1016/j.apsusc.2010.10.132
Abstract
Ba(Zr0.20Ti0.80)O3 (BZT) thin films are deposited on Pt(1 1 1)/Ti/SiO2/Si, MgO and ZrO2 buffered Pt(1 1 1)/Ti/SiO2/Si substrates by a sol–gel process. The BZT thin films directly grown on Pt(1 1 1)/Ti/SiO2/Si substrates exhibit highly (1 1 1) preferred orientation, while the films deposited on Pt(1 1 1)/Ti/SiO2/Si substrates with MgO and ZrO2 buffer layers show highly (1 1 0) preferred orientation. At 100 kHz, dielectric constants are 417, 311 and 321 for the BZT thin films grown on Pt(1 1 1)/Ti/SiO2/Si, MgO and ZrO2 buffered Pt(1 1 1)/Ti/SiO2/Si substrates, respectively. The difference in dielectric properties of three BZT films can be attributed to the series capacitance effect, interface conditions and their orientations.
Co-reporter:Xihong Hao, Jiwei Zhai, Jing Zhou, Zhenxing Yue, Jichun Yang, Wenguang Zhao, Shengli An
Journal of Alloys and Compounds 2011 Volume 509(Issue 2) pp:271-275
Publication Date(Web):12 January 2011
DOI:10.1016/j.jallcom.2010.07.200
In this paper, we report on the structure and electrical properties of lead zirconate (PbZrO3) thin films doped with barium (Ba2+) and strontium (Sr2+) deposited on platinum-buffered silicon substrates by a sol–gel method. Effects of Ba2+ and Sr2+ dopants on microstructure and electrical properties of the PbZrO3 antiferroelectric thin films were investigated in details. X-ray diffraction patterns and scanning electron microscope micrographs illustrated that orientation and surface microstructure of these antiferroelectric films were dopant-dependent. The dielectric measurements showed that Sr2+ doping stabilized the antiferroelectric phase, while Ba2+ doping destabilized the antiferroelectric phase. It was also found that fatigue property of the antiferroelectric PbZrO3 thin films was improved remarkably by the dopants.Research highlights▶ The structure and electrical properties of lead zirconate (PbZrO3) thin films could be tailored by barium (Ba2+) and strontium (Sr2+) doping. ▶ Sr2+ doping stabilized the antiferroelectric phase, while Ba2+ doping destabilized the antiferroelectric phase. ▶ The fatigue property of the antiferroelectric PbZrO3 thin films was improved remarkably by Ba2+ and Sr2+ dopants.
Co-reporter:Fang Fu, Jiwei Zhai, Zhengkui Xu, Wangfeng Bai, Xi Yao
Solid State Sciences 2011 Volume 13(Issue 5) pp:934-937
Publication Date(Web):May 2011
DOI:10.1016/j.solidstatesciences.2011.02.014
Textured (1 − x)(0.94Na0.5Bi0.5TiO3 − 0.06BaTiO3) − xK0.5Na0.5NbO3 (abbreviated as NBT–BT–KNN) thick film on platinum substrate was prepared via tape casting method. The structure and electrical properties of the thick films were investigated. The results show that the thick films possess typical polycrystalline perovskite structures and the orientation degree reached to 75%. The remnant polarization (Pr) and coercive field (Ec) were optimized to 11.2 μC/cm2 and 12.8 kV/cm for x = 0.02 thick film. The dielectric properties of NBT–BT–KNN thick films as a function of temperature were also investigated. With the addition of KNN, the Td (depolarization temperature) and TC (Curie temperature) are all decreased. Meanwhile, the dielectric constant is increased with the addition of the KNN at room temperature. The piezoelectric constant of the thick film was calculated from unipolar electric field-induced strain curve. With the addition of KNN, the d33 value increased and reached to the maximum value of 349 pm/V for x = 0.02 thick film.
Co-reporter:Mingwei Zhang, Jiwei Zhai, Bo Shen, Xi Yao
Materials Chemistry and Physics 2011 Volume 128(Issue 3) pp:525-529
Publication Date(Web):15 August 2011
DOI:10.1016/j.matchemphys.2011.03.043
Ba0.5Sr0.5TiO3–BaWO4 ceramics with transition metal ions acceptor Mn and donor V-doping are prepared by solid-state route and characterized systematically in terms of their phase compositions, microstructure and microwave dielectric properties. These dopants had a strong effect on microstructures of the ceramics. Curie temperatures of all samples are shifted and their dielectric peaks were broadened. Meanwhile, loss tangent of either the acceptor (Mn-doped) or the donor (V-doped) doped samples decreased at both low frequency (10 kHz) and microwave frequency at room temperature. Especially, the doped samples exhibit promising microwave dielectric properties, making them suitable candidates for applications in electrically tunable microwave devices.Highlights► Difference of structure and properties between acceptor and donor doped samples were analyzed. ► All the doped samples decrease loss tangent availably both at low frequency and high frequency. ► Doped samples have high Q value, acceptable tunability and appropriated value of permittivity.
Co-reporter:Fang Fu, Jiwei Zhai, Zhengkui Xu, Bo Shen, Xi Yao
Solid State Communications 2011 Volume 151(Issue 2) pp:120-122
Publication Date(Web):January 2011
DOI:10.1016/j.ssc.2010.11.011
BaTiO3 thick film with a (h00) grain orientation was fabricated by the template grain growth method. The thick film had a single phase of perovskite, with a Lotgering’s factor of as high as 86%. The ferroelectric properties of the thick film were investigated. The saturate and remnant polarizations of the grain orientated thick film were 37.3 and 14.4 μC/cm2, respectively. The temperature dependence of the dielectric constant and loss tangent were also evaluated. The Curie temperature of the thick film shifted to a high temperature as compared to that of its randomly orientated counterpart. This could be attributed to the large grain size of the grain oriented thick film. The piezoelectric properties of the thick film were characterized by the relationship of the unipolar strain and applied electric field. The piezoelectric constant d33∗ of the grain oriented thick film was 154 pm/V, which was higher than that of a randomly oriented film (d33∗=100pm/V) by more than 50%.Research highlights► (h00)-oriented BT thick film with a high orientation degree of 86% is prepared by the TGG method. ► The ferroelectric properties were enhanced by using the grain orientation technology. ► The piezoelectric constant improved 54% by grain orientation.
Co-reporter:Xiaolei Fang;Bo Shen;Xi Yao
Journal of Sol-Gel Science and Technology 2011 Volume 58( Issue 1) pp:1-5
Publication Date(Web):2011 April
DOI:10.1007/s10971-010-2346-y
(Na0.5Bi0.5)0.94Ba0.06TiO3 thin films were deposited on Pt/Ti/SiO2/Si (111) substrates by a sol–gel process. The precursor solutions for spin-coating were prepared using ammonia solution and ethanolamine as a ligand, respectively. The phase structure, ferroelectric and dielectric properties were investigated. The X-ray diffraction (XRD) pattern indicated that the thin films are polycrystalline structure. The surface and cross sectional morphology of the thin films was observed by a field-emission scanning electron microscope (FESEM). The dielectric constant and dielectric loss of thin films with ammonia solution as a ligand (NBT-BT-A) are about 600 and 0.03 at 10 kHz at room temperature, while the values for thin films with ethanolamine as a ligand (NBT-BT-E) are about 270 and 0.03. NBT-BT-A film showed a much lower leakage current. The hysteresis loops for NBT-BT-A thin films at an applied electric field of 400 kV/cm were acquired with a higher saturation polarization and a much smaller coercive field comparing to the NBT-BT-E thin films.
Co-reporter:Xihong Hao, Jiwei Zhai, Zhenxing Yue, Jing Zhou, Xiwen Song, Jichun Yang, Shengli An
Materials Research Bulletin 2011 46(3) pp: 420-423
Publication Date(Web):
DOI:10.1016/j.materresbull.2010.12.005
Co-reporter:Qiwei Zhang, Peng Qi, Jiwei Zhai, Fang Fu, Xi Yao
Materials Research Bulletin 2011 46(5) pp: 738-742
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.01.011
Co-reporter:Mingwei Zhang, Jiwei Zhai, Bo Shen, Xi Yao
Materials Research Bulletin 2011 46(7) pp: 1045-1050
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.03.009
Co-reporter:Mingwei Zhang, Jiwei Zhai, Jingji Zhang, Haitao Jiang, Xi Yao
Materials Research Bulletin 2011 46(7) pp: 1102-1106
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.02.046
Co-reporter:Changzhou Wang, Jiwei Zhai, Zhitang Song, Fei Shang, Xi Yao
Applied Surface Science 2010 Volume 257(Issue 3) pp:949-953
Publication Date(Web):15 November 2010
DOI:10.1016/j.apsusc.2010.07.099
Abstract
The amorphous-to-crystalline transition of Ge/Sb2Te3 nanocomposite multilayer films with various thickness ratios of Ge to Sb2Te3 were investigated by utilizing in situ temperature-dependent film resistance measurements. The crystallization temperature and activation energy for the crystallization of the multilayer films increased with the increase in thickness ratio of Ge to Sb2Te3. The difference in sheet resistance between amorphous and crystalline states could reach as high as 104 Ω/□. The crystallization temperature and activation energy for the crystallization of Ge/Sb2Te3 nanocomposite multilayer films was proved to be larger than that of conventional Ge2Sb2Te5 film, which ensures a better data retention for phase-change random access memory (PCRAM) use. A data retention temperature for 10 years of the amorphous state [Ge (2 nm)/Sb2Te3 (3 nm)]40 film was estimated to be 165 °C. Transmission electron microscopy (TEM) images revealed that Ge/Sb2Te3 nanocomposite multilayer films had layered structures with clear interfaces.
Co-reporter:Changzhou Wang, Jiwei Zhai, Suyuan Bai, Xi Yao
Materials Letters 2010 Volume 64(Issue 21) pp:2314-2316
Publication Date(Web):15 November 2010
DOI:10.1016/j.matlet.2010.07.059
Crystallization temperature of nitrogen-doped Sb2Te3 (ST) thin films increased with increasing nitrogen doping concentration, which indicates that the long-term stability of the metastable amorphous state can be improved by nitrogen doping. The root-mean-square (rms) roughness values of the films showed a significant decrease with nitrogen doping. Thermal conductivity of nitrogen-doped ST thin films was measured using a transient thermoreflectance (TTR) technique. It was found that the thermal conductivity decreased with increasing nitrogen doping concentration and increased with increasing annealing temperature. Nitrogen-doped ST thin films are suitable phase-change materials for low programming power consumption applications of phase-change random access memory (PCRAM).
Co-reporter:Lina Gao, Jiwei Zhai, Sannian Song, Xi Yao
Materials Chemistry and Physics 2010 Volume 124(Issue 1) pp:192-195
Publication Date(Web):1 November 2010
DOI:10.1016/j.matchemphys.2010.06.018
The orientation-dependent out-of-plane dielectric properties of barium stannate titanate (Ba(Sn0.15Ti0.85)O3 (BTS)) thin films prepared by sol–gel method were investigated. Films with (1 0 0), (1 1 0), and (1 1 1) orientation were grown on LaNiO3-buffered (1 0 0), (1 1 0), and (1 1 1) LaAlO3 (LAO) single-crystal substrates, respectively. The different temperature of the dielectric constant maximum (Tm) of the BTS thin films with different orientation was believed to be attributing to stress inside the films. Films with the (1 1 1) orientation had higher relative dielectric constant and tunability than (1 0 0)- and (1 1 0)-oriented films. This difference in dielectric properties in these three kinds of oriented BTS films may be attributed to change in the direction and magnitude of electric polarization in orientation engineered BTS films and stress in the films.
Co-reporter:Mingwei Zhang, Jiwei Zhai, Haitao Jiang, Jingji Zhang, Xi Yao
Materials Science and Engineering: B 2010 Volume 172(Issue 3) pp:311-316
Publication Date(Web):15 September 2010
DOI:10.1016/j.mseb.2010.06.018
Co-reporter:Qunping Jia, Bo Shen, Xihong Hao, Jiwei Zhai, Xi Yao
Thin Solid Films 2010 Volume 518(Issue 24) pp:e89-e92
Publication Date(Web):1 October 2010
DOI:10.1016/j.tsf.2010.03.110
Via the sol–gel process, compositionally graded and homogeneous BaZrxTi1 − xO3 (BZT) thin films were grown on (100)-oriented LaNiO3 (LNO)/Si substrates, respectively. The compositionally graded BZT thin film consisted of BaZr0.05Ti0.95O3 (BZT5), BaZr0.10Ti0.90O3 (BZT10) and BaZr0.15Ti0.85O3 (BZT15). Homogeneous thin films of above three compositions were fabricated for comparison. X-ray diffraction measurements show all the BZT thin films exhibit a single perovskite phase with highly (100)-preferred orientation. The temperature-dependent dielectric properties of these films show typical diffuse phase transition, and the phase transition temperature are all lower than −35 °C. A prominent increase of the dielectric constant and a more aligned surface morphology is observed in the compositionally graded thin film compared to the homogeneous samples.
Co-reporter:Mingwei Zhang, Jiwei Zhai, Xi Yao
Materials Research Bulletin 2010 45(12) pp: 1990-1995
Publication Date(Web):
DOI:10.1016/j.materresbull.2010.08.004
Co-reporter:Jingji Zhang, Jiwei Zhai, Xiujian Chou, Jun Shao, Xiang Lu, Xi Yao
Acta Materialia 2009 Volume 57(Issue 15) pp:4491-4499
Publication Date(Web):September 2009
DOI:10.1016/j.actamat.2009.06.011
Abstract
The dielectric properties, infrared (IR) dielectric response and Raman spectra of tunable microwave (MW) Ba1−xSrxTiO3 (x = 0.4, 0.5, 0.6 and 0.7) ceramics were studied systematically as functions of composition and temperature. It was found that, with increasing the content of Sr from 40% to 70%, the permittivity of the Ba1−xSrxTiO3 ceramics decreased from 7200 to 640 while the dielectric tunability decreased from 50.1% to 5.4% measured at 10 kHz. It is particularly interesting that the MW dielectric loss tangent was significantly decreased from 1.5 × 10−2 to 7.4 × 10−4. Complex permittivity spectra obtained by fitting the infrared data were also extrapolated to MW frequency and compared with the dielectric data near 1 GHz. For the samples with x = 0.4 and x = 0.5, the dielectric loss measured at ∼1 GHz was much higher than that calculated at 10 GHz, which is presumably due to the Debye-type dielectric relaxation in GHz region. However, the dielectric loss of the samples with x = 0.6 and x = 0.7, extrapolated from IR range, was in agreement with that measured at MW frequency. Low-temperature Raman scattering showed that the band at 760 cm−1 assigned to the Ti−O3 torsional mode markedly sharpens and shifts upward with increasing content of Sr. This is an indication that the bonding between cations and anions was tightened due to the substitution of Ba with Sr, which explains well the decrease in dielectric permittivity, loss and tunability with increasing concentration of Sr.
Co-reporter:Peng Li, Baihui Liu, Bo Shen, Jiwei Zhai, Lingyu Li, Huarong Zeng
Ceramics International (January 2017) Volume 43(Issue 1) pp:
Publication Date(Web):January 2017
DOI:10.1016/j.ceramint.2016.10.033
In this paper, a novel system of lead-free piezoelectric ceramics 0.94(Bi0.5Na0.5)TiO3−0.06BaTiO3-xBi4Ti3O12 (abbreviated as BNT-BT-xBiT) were prepared by the solid-state reaction method. The effects of Bi4Ti3O12 dopant on the strain behavior, dielectric, ferroelectric and piezoelectric performance of BNT-BT ceramics were systematically investigated. A optimal strain value of ~0.37% was achieved around the critical composition of x=6 wt% which corresponds to a normalized strain (Smax/Emax) of 465 pm/V. The large strain response in this sample is mainly originated from two aspects: one is that BiT addition induced ferroelectric-to-relaxor phase transition evidenced by “pinched” ferroelectric hysteresis loops and vanished negative strain of bipolar strain loops as well as downward shift of TF-R; the other is that the small-sized nanodomains (or polar nanoregions) facilitate the domain switching and domain wall motion with an applied electric field, which lead to large external contribution to strain response. These results indicate that BNT-BT-xBiT piezoelectric ceramics with large strain response may be a promising lead-free material for actuator application.
Co-reporter:Xing Liu, Jiwei Zhai, Bo Shen, Feng Li, Yang Zhang, Peng Li, Baihui Liu
Journal of the European Ceramic Society (April 2017) Volume 37(Issue 4) pp:
Publication Date(Web):April 2017
DOI:10.1016/j.jeurceramsoc.2016.12.020
In this work, the (1-x)(0.8Na0.5Bi0.5TiO3-0.2K0.5Bi0.5TiO3)-xSrTiO3 (NKBT-xST) incipient piezoelectric ceramics with x = 0–0.07 (0ST-7ST) were prepared by the solid-state reaction method and their structural transformation and electromechanical properties were investigated as a function of ST content. As the ST content increases, the long-range ferroelectric order is disrupted, and the ferroelectric-relaxor phase transition temperature (TFR) shifts to around room temperature for NKBT-5ST ceramics, accompanied by a relatively high electrostrain of 0.3% at 6 kV/mm. The large strain response associated with the vanished ferroelectric properties around TFR can be attributed to the reversible relaxor-ferroelectric phase transition. The electric-field-temperature (E-T) phase diagrams were established, and the transition between the two field-induced long-range ferroelectric states were found to take place via a two-step switching process through an intermediate relaxor state. The threshold electric field to trigger the conversion between ferroelectric state and relaxor state depends strongly on the dynamics of polarization relaxation, which is influenced by temperature and composition.
Co-reporter:Shiyu Chen, Weihua Wu, Jiwei Zhai, Sannian Song, Zhitang Song
Materials Science and Engineering: B (April 2017) Volume 218() pp:
Publication Date(Web):April 2017
DOI:10.1016/j.mseb.2017.02.002
•Sb7Te3 (ST) provides a fast crystallization speed, low melting temperature.•The Sb7Te3/ZnSb films exhibits faster crystallization speed, high thermal stability.•The calculated temperature for 10-year data retention is about 127 oC.•The Sb7Te3/ZnSb multilayer configuration with low power consumption.Phase-change memory is regard as one of the most promising candidates for the next-generation non-volatile memory. In this work, we proposed a Sb7Te3/ZnSb multilayer thin films to improve the thermal stability of Sb-rich Sb3Te7. The sheet resistance ratio between amorphous and crystalline states reached up to 4 orders of magnitude. With regard to the thermal stability, the calculated temperature for 10-year data retention is about 127 °C. The threshold current and threshold voltage of a cell based on Sb7Te3/ZnSb are 6.9 μA and 1.9 V, respectively. The lower RESET power is presented in the PCM cells of Sb7Te3/ZnSb films, benefiting from its high resistivity.
Co-reporter:Ruirui Liu, Pengzhi Wu, Zifang He, Jiwei Zhai, Xinyi Liu, Tianshu Lai
Thin Solid Films (1 March 2017) Volume 625() pp:
Publication Date(Web):1 March 2017
DOI:10.1016/j.tsf.2017.01.041
•The stability of [SS(10 nm)-GT(40 nm)]1 is better than that of [SS(2 nm)-GT(10 nm)]4.•The pre-precipitated Sb phase affects the properties of the film.•The pre-precipitated Sb phase and GeTe interact in the interface.•The interaction in the interface accounts for the different stability of the films.•Very fast phase change speed is found in SnSb4-GeTe (SS-GT) thin film.In this study, two series of superlattice-like (SLL) SnSb4-GeTe thin films with mono-period and multi-period stacks are fabricated. [SnSb4(10 nm)-GeTe(40 nm)]1 and [SnSb4(2 nm)-GeTe(10 nm)]4 thin films are the most representative ones in terms of mono-period and multi-period stacking group, showing good crystallization speed and distinct thermal stability. The results illustrate that the similar crystallization speed (< 5 ns) exists in both [SnSb4(10 nm)-GeTe(40 nm)]1 and [SnSb4(2 nm)-GeTe(10 nm)]4 thin films. In terms of thermal stability, the ten years data retention of [SnSb4(2 nm)-GeTe(10 nm)]4 and [SnSb4(10 nm)-GeTe(40 nm)]1 thin film are 102.3 °C and 149.5 °C respectively. The difference of the stability mainly derives from the different stacking number of SnSb4-GeTe interface, giving rise to the different degrees of interaction between pre-precipitates Sb (crystallization) and GeTe (amorphous).
Co-reporter:Haitao Wang, Jinhua Liu, Jiwei Zhai, Bo Shen, Zhongbin Pan, Ke Yang, Jingran Liu
Ceramics International (1 April 2017) Volume 43(Issue 5) pp:
Publication Date(Web):1 April 2017
DOI:10.1016/j.ceramint.2016.12.042
Phase evolution, dielectric properties, breakdown strength, and energy-storage performance were studied by varying K2O content in K2O-BaO-Nb2O5-SiO2 glass-ceramics. It was found that dielectric loss with the increase of K2O content increases owing to the un-crystallized K2O into the glass network, while dielectric breakdown strength firstly increases and then decreases due to the competition between two physical mechanisms, i.e., interfacial polarization and bridging-oxygen bond broken by the non-bridging oxygen ions. With the increase of K2O content, energy-storage density firstly increased up to 12.06±0.69 J/cm3 with a high breakdown strength of 1973 kV/cm, and then decreased. Also, the discharged efficiency is obtained as a high value of 92% from P-E hysteresis loops.
Co-reporter:Zhongbin Pan, Jiwei Zhai and Bo Shen
Journal of Materials Chemistry A 2017 - vol. 5(Issue 29) pp:NaN15226-15226
Publication Date(Web):2017/06/27
DOI:10.1039/C7TA03846A
Polymer nanocomposites with high energy density have potential applications in advanced electronics and electric power systems. The inevitable electrical mismatch between nanofillers and the polymer matrix could compromise the energy storage capability and dielectric properties of the polymer nanocomposites. Herein, novel core–double-shell structured BaTiO3@TiO2@Al2O3 nanofibers (BT@TO@AO NFs) were prepared via a one step method, and were incorporated into poly(vinylidene fluoride) (PVDF). The novel design of gradually varying the multilayer hierarchical interface was advantageous to alleviating the local electric field and electric current density intensification in the filler/polymer system. As compared with the nanocomposites loaded with BT NFs and BT@TO NFs, the nanocomposites filled with BT@TO@AO NFs exhibit much decreased dielectric loss, enhanced breakdown strength, and suppressed leakage current densities. Simulations were carried out to verify that the new core–double-shell structure significantly enhances the breakdown strength and energy density. As a result, the nanocomposite films loaded with 3.6 vol% BT@TO@AO NFs show a maximum energy storage density (Ue) of 14.84 J cm−3 at 450 MV m−1, which is about twelve times greater than that of biaxially oriented polypropylene (BOPP) (≈1.2 J cm−3 at 640 MV m−1). Moreover, the nanocomposite exhibits a superior power density of 4.7 MW cm−3 and an ultra-fast discharge speed of 0.37 μs. This research opens up a convenient and effective way for designing high-performance dielectric polymer nanocomposites.
Co-reporter:Wangfeng Bai, Daqin Chen, Peng Zheng, Bo Shen, Jiwei Zhai and Zhenguo Ji
Dalton Transactions 2016 - vol. 45(Issue 20) pp:NaN8586-8586
Publication Date(Web):2016/04/13
DOI:10.1039/C6DT00906A
In this study, a lead-free ceramic system comprising (0.94 − x)Bi0.5Na0.5TiO3–0.06BaTiO3–xBi(Zn0.5Ti0.5)O3 (BNT–BT–BZT) was designed and prepared by a conventional solid-state reaction method. The effect of the addition of BZT on the phase transition characteristics and associated electromechanical properties of BNT–BT was systematically discussed and a schematic phase diagram was established. The addition of BZT had a strong impact on the phase transition as well as the strain and piezoelectric activity. The phase coexistence, which involves ferroelectric rhombohedral-relaxor pseudocubic phases, can be driven by modification with BZT and increases in temperature and can be confirmed by XRD measurements, analysis of Raman spectra and temperature-dependent changes in polarization and strain hysteresis loops. Accompanied by a shift in the ferroelectric-to-relaxor temperature TF–R to below room temperature on the addition of BZT, a compositionally induced ferroelectric-to-relaxor phase transition occurred, which gave rise to a large strain of 0.33% with a normalized strain Smax/Emax of 550 pm V−1 at the critical BZT content x of 0.0275. The results were closely correlated with the composition and dependence on temperature of the phase transition, which significantly influenced the electromechanical properties, and the origin of the large strain observed in the present system was also addressed in detail. As a result, the design principles provided in this study open the possibility of obtaining BNT-based lead-free ceramics with enhanced electromechanical properties for actuator applications.
Co-reporter:Shaohui Liu and Jiwei Zhai
Journal of Materials Chemistry A 2015 - vol. 3(Issue 4) pp:NaN1517-1517
Publication Date(Web):2014/11/11
DOI:10.1039/C4TA04455J
Compared to the spherical ceramic fillers, the one-dimensional ceramic fillers are more effective in enhancing the dielectric constant of the composites at low concentration because the depolarization factor is strongly dependent on the aspect ratio of the fillers. Moreover, their smaller specific surface can help to reduce the surface energy and thus prevent the nanofillers from agglomerating in the polymer matrix. The ceramic–polymer composites consisting of SrTiO3 nanofibers (ST NF) with a large aspect ratio prepared via electrospinning and modified by polyvinylpyrrolidone (PVP) as fillers and poly(vinylidene fluoride) (PVDF) as matrix have been fabricated by a solution casting method. The composites exhibit enhanced dielectric constant and reduced loss tangents at a low volume fraction of surface-modified ST NF. The composite containing 2.5 vol% of PVP modified ST NF exhibits an energy density as high as 6.8 J cm−3 at 3800 kV cm−1, which is more than double of the pure PVDF of 2.8 J cm−3 at 4000 kV cm−1. Moreover, the efficiency of the composites with 2.5 vol% PVP modified ST NF is higher than 85% at electric fields below 1000 kV cm−1 and still higher than 60% at an electric field of 3800 kV cm−1. Such significant enhancement is closely related to combined effects of the surface modification, large aspect ratio and paraelectric behavior of the ST NF.
Co-reporter:Shaohui Liu, Shuangxi Xue, Wenqin Zhang, Jiwei Zhai and Guohua Chen
Journal of Materials Chemistry A 2014 - vol. 2(Issue 42) pp:NaN18046-18046
Publication Date(Web):2014/09/10
DOI:10.1039/C4TA04051A
Polymer composite flexible films with high dielectric constant are highly desirable in electronic and electrical industry. Higher loading of the ceramic fillers is usually needed in order to realize high dielectric constant. However, such composites exhibit low breakdown strength and poor mechanical and processing properties. In this work, by incorporating high aspect ratio surface-hydroxylated Ba0.6Sr0.4TiO3 nanotubes (BST NT) prepared via electrospinning into a polyvinylidene-fluoride (PVDF) matrix, PVDF nanocomposite flexible films with high dielectric constant have been successfully obtained. The nanocomposite containing 10 vol% BST NT-OH has a dielectric constant of 48.2 at 1 kHz, which is 6.1 times higher than that of the pure PVDF (7.9). The dielectric properties of the composites are closely related to the combined effects of the surface modification, large aspect ratio, high surface area and paraelectric polarization behavior of the BST NT.
Co-reporter:Zhongbin Pan, Lingmin Yao, Jiwei Zhai, Bo Shen, Shaohui Liu, Haitao Wang and Jinhua Liu
Journal of Materials Chemistry A 2016 - vol. 4(Issue 34) pp:NaN13264-13264
Publication Date(Web):2016/08/10
DOI:10.1039/C6TA05233A
Inorganic/polymer nanocomposites, using one-dimensional (1D) core–shell structure BaTiO3@Al2O3 nanofibers (BT@Al2O3 nfs) as fillers and poly(vinylidene fluoride) (PVDF) as the polymer matrix, have been prepared. The core–shell structure BT@Al2O3 nfs have been synthesized via coaxial electrospinning. The breakdown strength (Eb) and discharged energy density of the nanocomposites can be significantly improved by creating an insulating Al2O3 shell layer with moderate dielectric constant on the surfaces of BT nanofibers to form a moderate interfacial area. The Al2O3 shell layer could effectively confine the mobility of charge carriers, which reduces energy loss by reducing the Maxwell–Wagner–Sillars (MWS) interfacial polarization and space charge polarization between the fillers and the polymer matrix. As a result, the nanocomposite films filled with 5 vol% BT@Al2O3 nfs exhibit a excellent discharge energy density of 12.18 J cm−3 at 400 MV m−1, which is ≈254% over bare PVDF (4.8 J cm−3 at 350 MV m−1) and ≈1015% greater than the biaxially oriented polypropylenes (BOPP) (≈1.2 J cm−3 at 640 MV m−1). The work here indicates that this promising state-of-the-art method of preparing high energy density nanocomposites can be used in the next generation of dielectric capacitors.
Co-reporter:Lingyu Li, Yang Zhang, Wangfeng Bai, Bo Shen, Jiwei Zhai and Haydn Chen
Dalton Transactions 2015 - vol. 44(Issue 25) pp:NaN11625-11625
Publication Date(Web):2015/05/20
DOI:10.1039/C5DT01414J
Plate-like NaNbO3 (NN) templates have been successfully synthesized via a two-step molten salt method using K2CO3 as a raw material at 970 °C, which is below the topochemical reaction temperature using Na2CO3 as the raw material (higher than 1000 °C). The synthesized plate-like NN particles have a higher aspect ratio with a thickness of 0.5–1 μm, a width of 5–10 μm and a length of 15–25 μm. In this process, we found that Na2CO3 or K2CO3 plays an important role in removing the (Bi2O2)2+ layers in the substitution process and the final composition is decided by the type of molten salt. Using KCl as molten salt and Na2CO3 or K2CO3 as raw material, the (Bi2O2)2+ layers could be removed by Na2CO3 or K2CO3 and K+ ions can be incorporated into the template during the topochemical reaction and thus (K, Na)NbO3 (KNN) plate-like particles can be fabricated. The growth process is reasonably elucidated by this growth mechanism.
Co-reporter:Yang Zhang, Lingyu Li, Bo Shen and Jiwei Zhai
Dalton Transactions 2015 - vol. 44(Issue 17) pp:NaN7802-7802
Publication Date(Web):2015/03/18
DOI:10.1039/C5DT00593K
(1 − x)(K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O3-xSrZrO3 ((1 − x)KNLNS-xSZ) lead free piezoelectric ceramics have been prepared by the conventional solid state reaction method, via adjusting the orthorhombic–tetragonal phase transition temperature to near room temperature with doping SrZrO3, and the effects of SrZrO3 content on polymorphic phase transition have been investigated. These results show that the phase structure of the ceramics was changed from orthorhombic to tetragonal at x ≥ 0.02 mol, and the orthorhombic–tetragonal phase transition temperature was modified to around room temperature with increasing SrZrO3. Remarkable piezoelectric and ferroelectric properties has been obtained in (1 − x)KNLNS-xSZ system with x = 0.02, which showed a piezoelectric parameter of d33 = 256 pC N−1, Curie temperature Tc = 270 °C, strain levels of 0.16% at 50 kV cm−1, remnant polarization Pr = 24.9 μC cm−2 and coercive field Ec = 10.6 kV cm−1.
