The effects of growth temperature, coating cycles on the structure, electrical and optical properties of ITO films were investigated, and the stability under high temperature, high temperature & high humidity and alkaline environments was focused. With increasing the growth temperature, the crystalline phase transforms from amorphous to crystalline. The surface morphology shows flat and dense structure. The thickness, sheet resistance and resistivity firstly decrease and then increase, and the optimal sheet resistance and resistivity is 7.6 Ω/sq and 1.1×10−4 Ω cm. The average visible transmittance of the ITO films and ITO glass exceeds 85% and 80%. The band gap increases from 3.75 eV to 3.95 eV. The electrical and optical properties of the ITO films are very stable after eight coating cycles. The growth temperature significantly affects the change rate of sheet resistance under high temperature, high temperature & high humidity and alkaline environments. However, the change rate of sheet resistance is stable and sight for eight coating cycles.

Ca0.28Ba0.72Nb2O6 (CBN28) ceramics with different content of CuO were prepared by the conventional ceramic fabrication technique. The effects of CuO content on the phase structure, microstructure, dielectric and ferroelectric properties of obtained CBN28 ceramics were investigated. XRD results showed that pure tungsten bronze structure was obtained in all ceramics and CuO additive could accelerate the phase formation at lower temperatures. The CuO aid was effective for the uniform grain size in CBN28 ceramics, as it could facilitate the sintering behavior and suppress the anisotropic growth behavior obviously. The dielectric and ferroelectric properties of CBN28 ceramics depended greatly on the CuO content. Curie temperature Tc and dielectric loss tanδ both shifted downward, whereas the maximum dielectric constant εm and the dielectric constant around room temperature εr all increased initially and then decreased as x increased from 0.1 to 0.4 wt%. Normal ferroelectric hysteresis loops could be observed in all compositions, and the remnant polarization Pr decreased gradually. It was found that the comprehensive electric performance was optimized in CBN28-0.2 wt% CuO ceramics: εr = 453, εm = 3,371, Tc = 226 °C, tanδ = 0.048, Pr = 4.72 μC/cm2 and Ec = 13.81 kV/cm, showed that CuO sintering aid could not only ameliorate the sintering behavior but also improve the electrical properties.

Effect of concentration, water content (molar ratio of the water and titanium) and pH value of the sol, and sintering temperatures and holding time on microstructure and dielectric properties of Na0.5La0.5Cu3Ti4O12 (NLCTO) ceramics by a sol–gel method were investigated in detail, respectively. It is found that the optimum concentration, the molar ratio of the water and titanium, and pH value of the sol were 1.00 mol/L, 11.0, and 0.3, respectively. The NLCTO ceramics sintered at 1,080 °C for 10 h exhibited more homogeneous microstructure, higher dielectric constant (about 1.1–1.8 × 104) and lower dielectric loss (about 0.051–0.064 at 1–10 kHz). The higher dielectric constant of the NLCTO ceramics might be due to the internal barrier layer capacitor effect. The NLCTO ceramics prepared by the sol–gel method showed two kinds of dielectric relaxation at higher temperature by electric modulus analysis, and two relaxation activation energy values were obtained.

Tin-doped indium oxide (ITO) ceramic targets with three types of grain size (<10, 10–20 and >20 μm) were prepared by controlling sintering process. It is found that all targets show polycrystalline structure and a rapid heating and short holding time contributes to refining grain size. The ITO films were deposited using these ITO targets with three types of grain sizes under dc and rf mode. The effects of grain size on the structural, electrical and optical properties of the as-deposited films were systematically investigated. The results indicate that all ITO films are the (222) preferred orientation, and the surface grain morphologies are round (dc mode) and triangular (rf mode). The sheet resistance, transmittance and uniformity of the ITO films are significantly impacted by the grain size. The small grain size (<10 μm) contributes to improving the uniformity of electrical and optical properties. The optimal uniformity of sheet resistance under dc and rf mode is about 13 and 10 %, respectively.

In this work, we report on the Pb(Mg1/3Nb2/3)O3–Pb(Zn1/3Nb2/3)O3–Pb(Zr0.52Ti0.48)O3 (PMN–PZN–PZT) ceramics with Ba(W0.5Cu0.5)O3 as the sintering aid that was manufactured in order to develop the low-temperature sintering materials for piezoelectric device applications. The phase transition, microstructure, dielectric, piezoelectric properties, and the temperature stability of the ceramics were investigated. The results showed that the addition of Ba(W0.5Cu0.5)O3 significantly improved the sintering temperature of PMN–PZN–PZT ceramics and could lower the sintering temperature from 1005 to 920 °C. Besides, the obtained Ba(W0.5Cu0.5)O3-doped ceramics sintered at 920 °C have optimized electrical properties, which are listed as follows: (Kp = 0.63, Qm = 1415 and d33 = 351 pC/N), and high depolarization temperature above 320 °C. These results indicated that this material was a promising candidate for high-power multilayer piezoelectric device applications.Research highlights▶ Addition of 0.13 wt.% Ba(W1/2Cu1/2)O3 content could lower the sintering temperature from 1005 to 920 °C. The ceramics sintered at 920 °C could achieve optimized electrical properties and temperature stability. This material has been satisfied with the requirements of high-power piezoelectric ceramic devices.

NaNbO3 (NN) powders were synthesized by hydrothermal (HT) and conventional solid-state (CMO) methods, the obtained fine powders were used to prepare ceramics through conventional sintering process. The effect of preparation methods on the phase structure, morphology, and microstructure were investigated. Electric and piezoelectric properties of NN ceramics were measured. Fine NN powders with smaller sizes and high crystallinity were obtained under suitable hydrothermal conditions (200 °C, 2.64 M NaOH concentration and heat preservation for 24 h). The different fingerprints of Raman spectra of samples could be attributed to the different phase structure of NN powders prepared by HT (O3 orthorhombic phase) and CMO (O1 orthorhombic phase) methods. In addition, the results illustrated that the sintering temperature of HT-synthesized ceramics was lower and compactness was better than that of CMO-synthesized ceramics. Notably, the HT-synthesized ceramics obtained better electrical properties than that of CMO-synthesized ceramics, which were as follows: d33 = 41 pC N−1, Kp = 0.30, ɛm = 1565 (1 kHz) and Tc = 378 °C.Research highlights▶ The main concentration of current hydrothermal methods about NN powders are on the conditions of the preparation process and the structure evolution from the solid reactant to the intermediate and final product, very few efforts have been made to study the properties of ceramics prepared by hydrothermal methods. ▶ Two different kinds of NN powders were synthesized for the property comparison via hydrothermal and conventional mixed-oxide methods in this study. The properties of the two different kinds of NN ceramics such as dielectricity and piezoelectricity were also detected. ▶ The results illustrated that the sintering temperature of HT-synthesized ceramics was lower and compactness was better than that of CMO-synthesized ceramics. What's more, the HT-synthesized ceramics obtained better electrical properties than that of CMO-synthesized ceramics.

Lead-free Sr2KxNa1−xNb5O15 (0.00 ≤ x ≤ 0.20) piezoelectric ceramics were prepared by two-step solid state reaction method. Pure tungsten bronze structure could be obtained in all ceramics and K substitution could accelerate the phase formation at lower temperatures. The lattice constant calculation indicated expansion of the unit cell and reduced distortion of the crystal structure with K substitution due to the bigger ionic size of K+ (1.64 Å) compared to that of Na+ (1.39 Å). Electrical properties of Sr2KxNa1−xNb5O15 ceramics greatly depended on the K content. Curie temperature Tc shifted downward, whereas the maximum dielectric constant ɛm and the degree of diffusion phase transition all increased initially and then decreased as K content increased, indicating that proper amount of K substitution with x between 0.05 and 0.10 could enhance the dielectric properties. All the ceramics showed an intermediate relaxor-like behavior between normal and ideal relaxor ferroelectrics according to the modified Curie–Weiss law. With increasing K content, the remnant polarization (Pr) decreased gradually and the coercive field (Ec) decreased initially and then increased. But normal ferroelectric hysteresis loops could be observed in all compositions. Besides, the underlying mechanism for variations of the electrical properties due to K substitution was explained in this work.Research highlights▶ Potassium was used partially substitute for sodium to obtain Sr2KxNa1−xNb5O15 ceramics using two-step solid state reaction method and traditional sintering process. ▶ K substitution could accelerate the phase formation and enhance the lattice constants. ▶ Electrical properties of Sr2KxNa1−xNb5O15 ceramics greatly depended on the K content. ▶ Proper amount of K substitution with x between 0.05 and 0.10 could enhance the dielectric properties.

Ta5+ doped strontium barium niobate (SBN) ceramics were synthesized by conventional oxide-mixed method. The phase structure, microstructure and dielectric properties of the ceramics with different Ta5+ contents and sintering temperatures were investigated. The X-ray diffraction patterns show that pure tungsten bronze structure can be obtained in all the ceramics. The ceramics with high relative density and a uniform and fine-grained microstructure could be obtained at 1430 °C. The grain size of Sr0.53Ba0.47Nb2−xTaxO6 decreased with increasing the Ta5+ content. The relaxor behavior observed in SBNT ceramics should be attributed to a cationic disorder induced by B-site substitutions, which was proved by linear fitting of the modified Curie–Weiss law. All samples are proved to be relaxor ferroelectric. It is also found that Curie temperature Tc and maximum dielectric constant ɛm both decrease with increasing Ta5+ content.

(0.05 − x)Pb(Mg1/3Nb2/3)O3–xPb(Sb1/3Nb2/3)O3–0.10Pb(Ni1/3Nb2/3)O3–0.85Pb(Zr1/2Ti1/2)O3 piezoelectric ceramics (abbreviated as PMN–PSN–PNN–PZT) were synthesized by traditional ceramics process. The effects of Pb(Sb1/3Nb2/3) content (abbreviated as PSN) on density, electrical properties and temperature stability of the ceramics were investigated in detail. The results showed that PMN–PNN–PZT ceramics with 0.015 PSN content sintered at 995 °C exhibited the favorable electrical properties and good temperature stability, which were listed as follows: d33 = 538 pC/N, kp = 0.81, Qm = 71, tan δ = 0.0095, ɛr = 3902, Δfr/fr20°C = −2.21% and Δkp/kp20°C = 3.61%. Meanwhile, the multilayer piezoelectric actuators with 65 piezoelectric layers and a thickness of 25 μm for each layer were fabricated using PMN–PSN–PNN–PZT by the tape-casting method and the ceramic/internal electrode co-firing technology. The multilayer piezoelectric actuators sintered at 995 °C exhibited larger displacement of 1.46 μm at the working voltage of 25 V.

Large platelet NaNbO3 (NN) seed crystals have been successfully synthesized from bismuth layer-structured ferroelectric Bi2.5Na3.5Nb5O18 (BNN) precursor by topochemical microcrystal conversion method. The effects of synthesis parameters, such as salt/oxide ratio, synthesis temperature and Na2CO3/BNN ratio, on the phase structure and morphology of both the BNN precursor and NN particles were investigated. The results show that large platelet BNN precursor with bismuth layer structure was obtained at 1125 °C with a salt-to-oxide weight ratio of 1.50:1. Besides, by optimizing the synthesis parameters, anisotropic NN seed crystals with pure perovskite phase were obtained at 975 °C with a Na2CO3/BNN molar ratio of 1.50:1. The obtained NN particles are very promising template for texturing (K, Na) NbO3-based ceramics by reactive-template grain growth method.

For the fabrication as step-down multilayer piezoelectric transformer, piezoelectric properties of Pb(Mg1/3Nb2/3)O3–Pb(Zn1/3Nb2/3)O3–Pb(Zr0.52Ti0.48)O3 (PMN–PZN–PZT) ceramics were optimized by ZnO–Li2CO3 (ZL) and Pb3O4 content. Effects of the additions on the structure, bulk density and electrical properties of ceramics were investigated. The results revealed that the proper additions of ZL with Pb3O4 content could modify the electrical properties of the PMN–PZN–PZT ceramics. The composition sintered at 995 °C with 0. 01 wt.% ZL and 0.10 wt.% Pb3O4 content showed higher values, which were listed as follows: d33 = 256 pC/N, Kp = 0.60, Qm = 1910, ɛr = 1032, tan δ = 0.0070 and r = 2.09 Ω. In addition, the step-down piezoelectric transformers with optimized PMN–PZN–PZT composites were fabricated and the characteristics as the output power and resistance loads were measured. Meanwhile, the step-down piezoelectric transformers sintered at 995 °C showed the favorable characteristics with a higher gain G of 0.204 and a lower temperature rise of 6 °C when the output power was 5 W, and the driving frequency were approximately constant (≈126 kHz) when the output power was from 5 to 13 W. Moreover, the maximum efficiency (90.2%) was obtained at load resistance of 10 Ω.

Pb(Zr,Ti)O3–Pb(Fe2/3W1/3)O3–Pb(Mn1/3Nb2/3)O3 (PZT–PFW–PMN) ceramics doped with BiFeO3 as sintering aids were manufactured in order to develop the low temperature sintering ceramics for piezoelectric devices, and phase structure, microstructure, dielectric, piezoelectric properties and the temperature stability were investigated. The results show that addition of BiFeO3 significantly improved the sinterability of PZT–PFW–PMN ceramics and could decrease the sintering temperature from 1200 to 1020 °C. The 0.20 wt.% BiFeO3-added PZT–PFW–PMN ceramics sintered at 1020 °C exhibited the favorable piezoelectric and dielectric properties, which were listed as follows: d33 = 309 pC/N, Kp = 0.59, Qm = 1551, tan δ = 0.0056, ɛr = 1723, Tc = 308 °C, Δfr/fr25°C = 0.331% and ΔKp/Kp25°C = −0.564%. The obtained properties make this composition to be a good candidate for high power piezoelectric devices.

(K0.5Na0.5)NbO3 (KNN) and 0.995(K0.5Na0.5)NbO3–0.005AETiO3 (AE = Mg, Ca, Sr, Ba) were successfully prepared by conventional ceramic processing and without the cold-isostatic-pressing (CIP) process. The effects of low AETiO3 (AET) concentration on crystal structure, density, dielectric and piezoelectric properties of the KNN based ceramics were evaluated. The results show that adding MgTiO3(MT) and BaTiO3(BT) to KNN can lead to the appearance of a trace amount of second phase(s), reduced density and deteriorated electrical properties. Adding CaTiO3(CT) and SrTiO3(ST) to KNN can promote densification and optimize electrical properties. Two phase transitions at Tt–o ( the temperature at which the phase transition from orthorhombic to tetragonal occurs) and Tc (the Curie temperature) were observed in KNN and all KNN–AET ceramics, by using differential scanning calorimetry (DSC) analysis and dielectric characterization. Adding AET to KNN caused the variations of Tt–o and Tc.

In this study, three kinds of central driving type piezoelectric transformers, Types A, B and C with different electrode distributing were investigated by using impedance analyses. With the increase of the input electrode area, the resonant resistance of input section decreased and the effective electromechanical coefficient increased. With the decrease of the length of the generator section, the resonant resistance of generator section increased and the effective electromechanical coefficient decreased. The voltage step-up ratio increased with the increase of the ratio of the input and output resonant resistance. The temperature rise of Type A was lower because the impedance matching between the load resistance and the output impedance was achieved. Taking into consideration of the mechanical quality factor (Qm), the output impedance (Zout) and the temperature rise (ΔT) of each transformer, Type A with the input electrode length ratio of 1:1:1 could be selected as the optimum structure to drive the LCD backlight.

For the fabrication as piezoelectric transformers, the density, microstructure, dielectric and piezoelectric properties of Pb(Mg1/3Nb2/3)O3–Pb(Zn1/3Nb2/3)O3–Pb(Zr0.52Ti0.48)O3 (PMN–PZN–PZT) ceramics as a function of calcining temperature and sintering temperature were investigated. In addition, the piezoelectric transformers with the composition of PMN–PZN–PZT were fabricated and the characteristics with various resistance loads were measured. The results indicated that the optimized properties of ceramics were obtained at calcining temperature of 800 °C and sintering temperature of 1020 °C, which were listed as follows: d33 = 249 pC/N, Kp = 0.57, Qm = 1954, ɛr = 1122 and tan δ = 0.0059. Meanwhile, piezoelectric transformers sintered at 1020 °C show the favorable characteristics with a higher step-up ratio of 145 and a lower temperature rise of 5 °C at 250 kΩ.

Piezoelectric powders and ceramics with a composition of Pb0.95Sr0.05 (Zr0.52Ti0.48) O3–Pb(Mg1 / 3Nb2 / 3)O3–Pb(Mn1 / 3Sb2 / 3)O3 (PZT–PMN–PMS) were prepared by the molten salt synthesis (MSS) method. It was found that the MSS method significantly improved the sinterability of PZT–PMN–PMS ceramics, resulting in a reduction of sintering temperature by about 100 °C compared to the conventional mixed-oxide (CMO) method. The optimum values of d33, Kp, Qm and tanδ were 244 pC/N, 0.53, 1034 and 0.0090, respectively, at calcination of 800 °C and sintering of 1050 °C.

•Ta0.05Ti0.95O2 samples with εr = 50000 and tanδ = 3.07% at 10 kHz were obtained.•The samples exhibit a relatively good temperature stability from −170 to 100 °C.•The samples also show a good frequency stability from 40 to 106 Hz.•The 2(Ta5+)Ti·→4(Ti3+)Ti′←Vo·· defect complex is introduced after Ta5+ doping.•Electron-pinned defect-dipoles are responsible for the observed giant permittivity.Colossal permittivity in tantalum-doped TiO2 (TaxTi1−xO2) (x = 1%, 2%, 3%, 4%, 5% and 6%) fabricated by the conventional solid-state reaction method in N2 atmosphere were achieved. Especially, by optimizing components and sintering temperatures, the dielectric loss could significantly decreased. The effects of Ta doping on their microstructure, dielectric properties, and temperature stability were revealed in detail. When the composition with x = 5% and sintered at 1400 °C, the dielectric constant reached to ∼30000 and the dielectric loss decreased to 3%. Interestingly, all the samples also exhibit good temperature stability of dielectric properties in a wide temperature range from 100 to 350 K. Based on XPS analysis, the formation of defect-dipole clusters, e.g. 2(Ta5+)Ti·→4(Ti3+)Ti′←Vo·· should be mainly responsible for the improved dielectric properties in tantalum-doped TiO2.

The crystal structures of the lead-free piezoelectric ceramics (K0.5Na0.5)NbO3 and (K0.5Na0.5)0.94Li0.06NbO3 prepared by a solid-state method were investigated using first-principles calculations. The calculated values of piezoelectricity were in good agreement with the experimental data. We found that the primary contribution to piezoelectricity in this material comes from the hybridization of the O 2p and Nb 4d orbitals, which causes a change in the Nb–O bond length and the distortion of the Nb–O octahedral structure. Analysis of the band structure and the total density of states revealed that Li-doped (K0.5Na0.5)NbO3 enhances hybridization of the O 2p and Nb 4d orbitals. This hybridization enhancement further reduces the Nb–O1 bond length and enhances the distortion of the Nb–O octahedron along the [001] direction, which may be the main reason for the improvement of the piezoelectric properties. In addition, the piezoelectric coefficients are calculated here, which show the same trend as the experimental results.