Antiferroelectric and ferrielectric liquid‐crystal display: Electrically controlled birefringence color switch as a new mode

Abstract— A mixture with intermediate biaxial (ferrielectric) smectic phases existing in a broad temperature range has been developed. At any temperature within this range, as well as in the antiferroelectric phase range, several birefringence color states can be switched stepwise by application of an electric field, and therefore a LC cell placed between crossed polarizers can display form several colors without the use of color filters. A very small time switching between color states (about 10 μsec) can be a basis for this new mode in display technology because several full‐color optical states can be realized in the same material (or in the mixture of materials). These possibilities were investigated both theoretically and experimentally.     

High energy-storage performance of lead-free AgNbO3 antiferroelectric ceramics fabricated via a facile approach

AgNbO₃ lead free AFE ceramics are considered as one of the promising alternatives to energy storage applications. In the majority of studies concerning the preparation of AgNbO₃ AFE ceramics, an oxygen atmosphere is required to achieve high performance, increasing the complexity of the fabrication process. Herein, a facile approach to preparing AgNbO₃ ceramics in the ambient air was reported, in which the AgNbO₃ ultrafine powder with stable perovskite structure was synthesized by hydrothermal method instead of the conventional ball milling process, leading to a lower temperature of phase formation and thus smaller grain size. The resulting ceramics sintered at 940 °C displayed high breakdown strength (216 kV/cm) and a recoverable energy density of 3.26 J/cm³ with efficiency of 53.5 %. Also, the high thermal stability of recoverable energy density (with minimal variation of ≤20 %) and efficiency (≤ 10 %) over 30–150℃, enables AgNbO₃ ceramics achieved to be a promising candidate for energy storage applications.     

Achieving high energy storage performance of Pb(Lu1/2Nb1/2)O3 antiferroelectric ceramics via equivalent A-site engineering

Manipulating the critical switching field between antiferroelectric (AFE) state and ferroelectric (FE) is an important concept for tuning the energy storage performance of AFEs. As one of the lead-based AFE systems, Pb(Lu_1/2Nb_1/2)O₃ promises high potential in the miniaturization of pulsed power capacitors, but the extremely high critical switching field and low induced saturated polarization demonstrate severe drawbacks with respect to temperature stability and flexibility. Here, A-site Ba²⁺ doping engineering is used to effectively reduce the critical switching field and improve the saturated polarization in Ba_xPb_1-x(Lu_1/2Nb_1/2)O₃ (0.01 ≤ x ≤ 0.08, abbreviated as xBa-PLN) ceramics. We found the AFE-FE phase transition can be occurred at 80ºC with a high energy storage density of 4.03 J/cm³ for Ba_0.06Pb_0.94(Lu_1/2Nb_1/2)O₃ ceramic. Our results show that Ba²⁺ additions destroy the antiparallel structure of AFE phase, and finally reduce the critical switching field, demonstrating a potential alternative to modulate the energy storage performance of AFEs.     

High breakdown strength and energy density in antiferroelectric PLZST ceramics with Al2O3 buffer

In this work, a new core-shell structure of antiferroelectric ceramic powder (Pb_0.97La_0.02Zr_0.85Sn_0.12Ti_0.03O₃-PLZST) coated with linear dielectric (Al₂O₃) has been successfully prepared to realize high energy density through tape-casting process. According to the experimental results of electron microscope, the sol-gel derived Al₂O₃ layer was uniformly coated on the PLZST particles and the Al₂O₃ layer can be taken as the buffer layer to effectively refine the grain growth as well. Therefore, the modified PLZST particles were fine and uniform compared with the pure PLZST. It was found that the buffer layer could undertake higher electric field and the electric field applied to PLZST particles was weakened based on finite element analysis, which can avoid the premature breakdown of PLZST. And the actual measured breakdown strength was significantly enhanced from 22.2 kV/mm to 35.5 kV/mm. Correspondingly, an extremely high recoverable energy storage density of 5.3 J/cm³ was obtained for PLZST with 0.5%wt Al₂O₃, an 204% enhancement over the pure PLZST ceramics (2.6 J/cm³), and the corresponding efficiency was up to 88.3%. In addition, impedance spectroscopy measurement was carried out to further confirm the better insulation of the ceramic with Al₂O₃ buffer.     

Conduction mechanism in antiferrolectric PbZrO3 thin films—analysis of charge carrier trapping phenomenon

Abstract

Antiferroelectric compositions, such as PbZrO₃, are attractive candidates in charge storage devices and actuator/transducer applications in MEMs technology. Thin films of PbZrO₃were deposited on Pt coated Si substrates by a pulsed excimer ablation process. The process of field induced ferroelectric phase switching involves the domain wall reorientation in the polycrystalline thin films. The presence of grain boundaries and various defects in the polycrystalline thin films acts as the pinning sources for the various domain walls. These defects capture the charge carriers in the presence of external applied field and hinders further switching of the dipoles in the domains, thereby increases the response times and threshold voltages for the devices operations. Understanding of the trapping phenomenon in these films is very essential. Using Lampert's theory of space charge limited conduction both shallow and deep trap energies were estimated approximately from charge transport analysis.     

Texture control and ferroelectric properties of Pb(Nb,Zr,Sn,Ti)O3 thin films prepared by chemical solution method

A chelating and spin-coating procedure was used to prepare antiferroelectric thin films of Pb_0.99Nb_0.02[(Zr_0.84Sn_0.16)_0.982Ti_0.018]_0.98O₃. By controlling substrate and thermal processing conditions, films with strong (100) and (111) textures, as well as without textures, were prepared. These antiferroelectric films showed the characteristic double hysteresis polarization vs. electric field loops. An orientation dependence of the critical field for the antiferroelectric-to-ferroelectric phase transition was also observed. In addition, when the applied voltage exceeded a critical level during the first “ramp up,” an abnormal reduction in the area of the hysteresis loop was noticed in the (100) and (111) textured films.     

Achieving excellent energy storage density of Pb0.97La0.02(ZrxSn0.05Ti0.95-x)O3 ceramics by the B-site modification

The applications of antiferroelectric (AFE) materials in miniaturized and integrated electronic devices are limited by their low energy density. To address the above issue, the antiferroelectricity of the reinforced material was designed to improve its AFE-ferroelectric (FE) phase transition under electric fields. In this present study, the composition of Zr⁴⁺ (0.72 Å) and Ti⁴⁺ (0.605 Å) at B-site of Pb_0.97La_0.02(Zr_xSn_0.05Ti_0.95-x)O₃ ceramics with orthogonal reflections are synthesized via the tape-casting method. These ceramics are modified to enhance their antiferroelectricity by reducing their tolerance factor. A recoverable energy storage density W_rec 12.1 J/cm³ was obtained for x = 0.93 under 376 kV/cm, which is superior value than reported until now in lead-based energy storage systems. Moreover, the discharge energy density can reach 10.23 J/cm³, and 90 % of which can be released within 5.66 μs. This work provides a new window and potential materials for further industrialization of pulse power capacitors.     

反铁电晶体Na3H（SeO4）2对称性和序参量

在反铁电晶体Na3H（SeO4）2顺电反铁电相变中,对称性所属点群也随之发生相应的改变。通过对X射线衍射实验结果的分析,我们认为Na3H（SeO4）2晶体反铁电相对称性所属点群为P2（C2）。选用轴矢量R作为序参量来描述Na3H（SeO4）2晶体反铁电相变中对称性的变化,应用居里原理,恰能得到Na3H（SeO4）2晶体反铁电相的正确对称性所属点群P2（C2）。     

Low temperature sintering of PLZST-based antiferroelectric ceramics with Al2O3 addition for energy storage applications

Antiferroelectric (AFE) materials have superior energy storage properties in high power multilayer ceramic capacitors (MLCCs). To adapt to the sintering temperature of inner metal electrodes with less palladium content, in this work, Al₂O₃ was added to Pb_0.95La_0.02Sr_0.02(Zr_0.50Sn_0.40Ti_0.10)O₃ (PLSZST) AFE ceramics, in an attempt to reduce the sintering temperature. Results of this study demonstrate that the optimal composition of PLSZST-0.8 wt% Al₂O₃ sintered at a lower temperature 1040 ℃, has a high recoverable energy density (W_re, 3.23 J/cm³) and a high efficiency (η, 90 %) at room temperature. It is also high in pulse discharge energy density (W_dis, 2.45 J/cm³), current density (1369 A/cm²), and has an extremely short period of discharge (less than 500 ns). In addition, both W_re and η demonstrate a good stability in temperature within a wide range of 30 ℃-100 ℃. In sum, this novel AFE composition has great potentials for energy storage applications such as high energy density MLCCs.