Ferroelectric phase transition characteristic and electrical conduction mechanism of the high Curie-point (TC) 0.15Pb(Mg1/3Nb2/3)O3−0.4PbHfO3−0.45PbTiO3 (PMN-PHT) piezoelectric ceramics were studied by the temperature dependent Raman spectra and electrical properties. Sole first-order ferroelectric phase transition is demonstrated by the thermal hysteresis behavior of the temperature dependent dielectric constant and the dramatic drop of the derivative of inverse dielectric constant ξ= d(1/εr)/dT around TC in the PMN-PHT ceramics. The temperature dependent Raman spectroscopy not only provides further evidence for the ferroelectric to paraelectric phase transition appearing around TC in the PMN-PHT ceramics, but also reveals the successive phase symmetry changes of the polar nanoregions (PNRs), in which apparent anomalies appear in the Raman peaks' wavenumber, wavenumber distance, intensity, intensity ratio, and line width of some selected Raman modes upon heating. Typical sole cole-cole circle is obtained for the PMN-PHT ceramics in the temperature range of 440–560 °C, based on which the activation energy (Ea) of the electrical conduction is calculated being ~1.2 eV. Such low value of Ea indicates that the oxygen vacancies formed in the PHT-PMN ceramics induced by the evaporation of Pb during the sintering process dominate the high-temperature extrinsic electrical conduction.

•High sintering capability Er3+-doped Na0.5Bi0.5TiO3 (NBT) nano particles were prepared by a simple hydrothermal method.•The Er3+-doped NBT ceramics prepared via the hydrothermal method exhibit pure perovskite structure and high densification.•The Er3+-doped NBT ceramics exhibit excellent upconversion and downconversion luminescence properties.Er3+-doped Na0.5Bi0.5TiO3 (Er-doped NBT) ceramics were prepared via a hydrothermal method. High sintering active Er-doped NBT nano cubic particles with perovskite structure were synthesized at hydrothermal condition of 200 °C for 24 h in 12 M NaOH solution, which were self-assembled via in situ crystallization mechanism by the initially as-grown nanowires. The Er-doped NBT ceramics sintered at 1100 °C for 2 h exhibit pure rhombohedral perovskite structure, high densification and rather homogenous microstructure morphology. Under 488 nm light excitation, the strong green emission peaks centering at 530 nm and 550 nm and the weak red emission peaks locating at 665 nm and 735 nm are excited, which can be attributed to the 2H11/2, 4S3/2, 4F9/2 and 4I9/2 → 4I15/2 transitions, respectively. The maximum emission intensity is obtained when the Er doping content reaches 1.0 mol%. A strong upconversion emission peak centering around 550 nm in green light range is excited under 800 nm light excitation, which is correlated with the 4S3/2 → 4I15/2 transition.

•Densified PNNHT/NZF composite ceramics were prepared by introducing nano-sized sintering aids via self-combustion method.•PNNHT/NZF exhibit homogenously dispersed and well isolated interfaces, and enhanced magnetoelectric properties.•Such performance relates to nano-sized sintering aids acting as blocking layers also introduced by self-combustion method.•Such ceramic processing is simple, feasible, and low cost, being applicable to other 0-3 particulate composite ceramics.The 0.55Pb(Ni1/3Nb2/3)O3-0.05PbHfO3-0.4PbTiO3/Ni0.875Zn0.125Fe2O4 (PNNHT/NZF) 0–3 particulate composite ceramics were prepared by the conventional solid-state reaction method via introducing the nano-sized WO3 and CuO sintering aids by the self-combustion method. Due to the introducing of nano-sized sintering aids, densified PNNHT/NZF composite ceramics are synthesized sintered at low sintering temperature. Furthermore, the nano-sized sintering aids act effectively as blocking layers, leading to compact composite ceramics with homogenously dispersed and isolated microstructure morphology, inhibiting inter-phase diffusion, avoiding interfacial chemical reaction, and achieving strong inter-phase coupling. Therefore, the synthesized PNNHT/NZF composite ceramics exhibit enhanced magnetoelectric properties.

•A PVDF-HFP additive specific to semitransparent perovskite films was developed.•The additive has significant effects on perovskite-film-morphology control.•The additive improves carrier lifetimes and decreases charge transport resistance.•The additive achieves over 30% PCE enhancement compared to control devices.Organometallic halide perovskite solar cells have considerable potential to be manufactured as low-cost and visible-light-semitransparent modules by reducing the thickness of the perovskite films for building-integrated photovoltaics. However, perovskite films often suffer from voids and roughness, inducing depressed photovoltaic performance, and this problem is even more severe for thinner perovskite films. Herein, a poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) additive is incorporated into CH3NH3PbI3 precursor solutions to control the crystal growth of a visible-light-semitransparent perovskite layer (thickness: ~150 nm) in a one-step deposition process. The characterization results show that the coverage and smoothness of the perovskite films can be significantly improved, and the perovskite crystal boundaries are also reduced by introducing a moderate amount of PVDF-HFP. When the precursor solution containing 12 mg/mL PVDF-HFP, the highest power conversion efficiencies of 10.6% and 8.8% (backward scan) is achieved for the photovoltaic devices with 80 and 20 nm-thick Au electrode, respectively, which is over 30% higher than that of the PVDF-HFP-free control. Time-resolved photoluminescence and electrochemical impedance spectroscopy characterizations further demonstrate that the PVDF-HFP additive can improve the carrier lifetimes and reduce the charge transfer resistance, which contributes to the enhanced photovoltaic performance. Thus, we propose a strategy specific to a high-quality visible-light-semitransparent perovskite layer and for high-performance perovskite solar-cell preparation.Download high-res image (353KB)Download full-size image

Domain configuration evolution with temperature of the unpoled [001]C-oriented 0.32Pb(In1/2Nb1/2)O3–0.345Pb(Mg1/3Nb2/3)O3–0.335PbTiO3 (0.32PIN–0.345PMN–0.335PT) single crystals was studied by the polarized light microscopy (PLM). The optical observation of the domain structures reveals the coexistence of polymorphic ferroelectric phases with mainly ferroelectric monoclinic phase at room temperature and the irreversible domain evolution upon thermal cycling, which induce the high piezoelectric response in such relaxor-based ferroelectric single crystals with the morphotropic phase boundary compositions combined with polarization rotation. The temperature dependent domain evolution and dielectric behavior demonstrate the successive temperature-induced second-order ferroelectric M phase to ferroelectric tetragonal (T) phase (FEM–FET) and first-order ferroelectric T phase to paraelectric cubic (C) phase (FET–PC) ferroelectric phase transitions in the unpoled 0.32PIN–0.345PMN–0.335PT single crystals. Two dielectric loss anomalies were detected around the dielectric anomaly below 100 °C in the poled 0.32PIN–0.345PMN–0.335PT single crystals, indicating that the FEM–FET phase transition can be correlated with two different ferroelectric phase transitions, one is MA–MC, and the other is MC–T phase transition. The FEM–FET phase transition was confirmed further by the energy density measurement. The temperature dependent piezoelectric properties proved that the working temperature of the 0.32PIN–0.345PMN–0.335PT single crystals can reach 130 °C, higher around 50 °C than the Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals, indicating their promising applications in transducers used at elevated temperatures.

•Intergranular corrosion suceptibility can be formed again in the Al-Mg-Si-Cu alloys during overaging.•The intergranular corrosion susceptibility results from the anodic disolution of the precipitation-free zones with the closely-neighbored grain boundary Q-phase precipitates acting as the continuous cathodes.•The closely-neighbored grain boundary precipitates is formed via their further growth by dissolving the adjacent matrix precipitates based on the Ostwald ripening process during the long-time overaging.Usually, underaged or peakaged Al-Mg-Si-Cu alloys are susceptible to intergranular corrosion (IGC), whereas overaging can eliminate the IGC susceptibility. However, it is found that the IGC susceptibility can be formed again when the alloys are heavily overaged further. The IGC susceptibility in the heavily overaged condition results from the anodic dissolution of the precipitation-free zones (PFZs) with the closely-neighbored grain boundary Q-phase (Al4Mg8Si7Cu2) precipitates acting as the continuous cathodes. The formation of the closely-neighbored grain boundary precipitates is attributed to their further growth via dissolving the adjacent matrix precipitates based on the Ostwald ripening process during the long-time overaging.

•NaOH is an available lypophobe in miniemulsion polymerization.•CdFe2O4-polymeric nano particles are well-formed by miniemulsion.•A smooth CdFe2O4 film is obtained before calcination.•The film shows well spinel structure at low calcination temperature.•The CdFe2O4-polymeric film exhibit high reaction activity.CdFe2O4-polymeric nanoparticles were prepared by inverse miniemulsion in order to achieve an acceptable grain size on the formed spin-coated film at a low calcination temperature. Sodium polyacrylate latex (PAANa) was synthesized by inverse miniemulsion polymerization using NaOH as a co-stabilizer. The effects of the NaOH content added to the inverse miniemulsion on the size and distribution of droplets and the latex particles were studied. The Cd-Fe salt droplets from the miniemulsion were absorbed by the PAANa latex particles, and the films formed by CdFe2O4-polymeric nanoparticles were characterized. The nucleation mechanism was characterized based on the ratio of the final number of latex particles to the initial number of droplets in a volume unit (Np/Nd). The increased NaOH dosage efficiently enhanced the stability of droplets, and Np/Nd approached 1. CdFe2O4-polymeric nanoparticles were formed using PAANa latex particles as a nano-reactor. The CdFe2O4-polymeric film prepared by inverse miniemulsion exhibits high reaction activity, as evidenced by the highly crystalline spinel structure formed at a low calcination temperature. The height of the film before and after calcination at 500 °C was 79 nm and 3.2 μm, respectively. The high reaction activity of CdFe2O4-polymeric nanoparticles can be successfully achieved by the inverse miniemulsion method.

•High transparency PLZnNZT ceramics were prepared by the hot-pressing sintering method.•The hot-pressing sintered ceramics exhibit dense, large-grained and perovskite structure.•The PLZnNZT ceramics exhibit excellent ferroelectric and piezoelectric properties.•The transmittance is 53% and the low-lying optical band gap energy Eg is 3.23 eV.•Three diffused Raman bands are observed by Raman spectroscopy.Lead-based Pb0.97La0.02(Zn1/3Nb2/3)0.3(Zr0.53Ti0.47)0.7O3 (PLZnNZT) transparent ceramics with the addition of 2 wt% excess PbO were prepared by hot-pressing sintering method. The hot-pressing sintered PLZnNZT ceramics exhibit dense and large-grained microstructure, and perovskite structure with distorted cubic-like symmetry. The ceramics exhibit normal ferroelectric-like dielectric behavior with slightly diffused ferroelectric phase transition characteristic. The PLZnNZT ceramics exhibit fully developed, symmetric and saturated P–E hysteresis loop and large piezoelectric constant d33, being 468 pC/N. The ceramics with 120 μm thickness exhibit maximum transmittance of 53% at 850 nm when Fresnel losses was not included, almost totally transparent in the mid IR region (2500–5600 nm), and low-lying optical band gap energy Eg of 3.23 eV. Three diffused Raman bands centering around 240 cm−1, 560 cm−1 and 750 cm−1 are observed by micro-Raman spectroscopy, which can be attributed to F2g [BO6] bending vibration, A1g [BO6] stretching vibration and “soft mode” mixed by the bending and stretching vibrations, respectively, confirming the normal ferroelectric-like characteristic.

•Oxide doping and B-site oxide mixing route are good for synthesizing ferroelectrics.•Pb(Fe1/4Sc1/4Nb1/2)O3/PFSN ceramics exhibit pure rhombohedral perovskite structure.•The MnO2- and Li2CO3-doped PFSN ceramics exhibit improved electrical properties.•The doped PFSN ceramics exhibit excellent pyroelectric property.•The doped PFSN ceramics exhibit promising applications for pyroelectric devices.Oxide doping and B-site oxide mixing route are superior in synthesizing complex perovskite structure ferroelectric ceramics, in which the oxide-doped Pb(Fe1/4Sc1/4Nb1/2)O3 (PFSN) ceramics exhibit phase-pure rhombohedral perovskite structure, high relative density and excellent dielectric properties. The MnO2- and Li2CO3-doped PFSN ceramics exhibit large pyroelectric coefficient, being 518.9 and 578.8 μC/K m2 at room temperature, respectively. The calculated pyroelectric figures of merit Fd and Fv exhibit excellent frequency stability and maintain almost stable within 100–2000 Hz. The pyroelectric coefficient and the calculated pyroelectric figures of merit increase greatly with the increase of temperature, which deserves further research to improve their temperature stability. Such investigations reveal that high-performance pyroelectric materials can be prepared by oxide doping via the B-site oxide mixing route in the synthesis of PFSN-based ceramics.