弛豫铁电体的微畴-宏畴转变与生长动力学

制备了铅基弛豫铁电体0.9 Pb(Mg1/3Nb2/3)O3-0.1 PbTiO3和Pb(Zn1/3Nb2/3)O3基陶瓷.利用修正的局域冻结玻璃模型研究了弛豫铁电体微畴-宏畴转变动力学和微畴生长动力学，结果表明,微畴-宏畴转变过程是量子化的过程，微畴-宏畴转变的驱动力主要是热驱动力和能量驱动力，微畴-宏畴转变稳定性由活化能和状态数来判断，而微畴生长动力学的稳定性可以用稳定性判据值大小确定.     

A Molecular Ferroelectric Showing Room‐Temperature Record‐Fast Switching of Spontaneous Polarization

Fast switching of spontaneous polarization (P_s) is one of the most essential requirements for ferroelectrics used in the field of data storage. However, in contrast to inorganic counterparts, the low operating frequency (<500 Hz) for molecular ferroelectrics severely hinders their large‐scale applications. Herein, for the first time, we achieved the room‐temperature fastest switching of the P_s in a new molecular ferroelectric, N‐methylmorpholinium trinitrophenolate ( 1 ), which displays notable ferroelectricity (P_s=3.2 μc cm^?2). Strikingly, electric polarizations of 1 have been switched under a record‐high frequency of 263 kHz, and this performance remains stable without any obvious fatigue after ca. 2×10⁵ switching cycles. To our knowledge, 1 is the first organic ferroelectric to switch polarization at such a high operating frequency, exceeding the majority of organic ferroelectrics, which opens up new possibilities for its potential in the field of non‐volatile memory.     

An acetic acid/water based sol-gel PZT process I: Modification of Zr and Ti alkoxides with acetic acid

The chemical reactions underlying the formation of a water based alkoxide sol gel solution for lead zirconate titanate thin films have been evaluated using infra-red spectroscopy and viscosity measurements. Titanium isopropoxide and zirconium propoxide are modified by acetic acid in order to use water as a solvent. Substitution reactions initially take place with the formation of titanium or zirconium alkoxide acetate and alcohol. The titanium or zirconium alkoxide acetate gradually associate through the formation of M-O-M linkages to increase the viscosity of the solution.     

Quantum chemistry of ferroelectric solids: Electronic structures and peculiar behavior of zero‐dimensional K3H(SO4)2‐like materials

The main problems of quantum chemistry of H‐bonded ferroelectrics are treated using the zero‐dimensional K₃H(SO₄)₂‐like crystals as suitable examples. Various quantum chemical approaches and computational procedures are applied to evaluate the Ising model coupling parameters that determine different thermodynamic and dielectric properties of these materials. The calculated Ising parameters are employed to describe the peculiarities of ferroelectric behavior of the K₃H(SO₄)₂ family crystals in the framework of mean field approximation. The problems related to the H‐bond proton (deuteron) tunneling are also discussed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Cell Volume Effect on the Ferroelectric Stability of Perovskite Oxides PbTiO3 and BaTiO3 from First Principle Calculation

Electronic structure of ferroelectric PbTiO3 and BaTiO3 is calculated by the full potential linearized augmented plane wave method. The total energy as a function of the displacement of Ti-cation is obtained for PbTiO3 and BaTiO3 at different cell volumes. At experimental cell volume, Ti-displacement lowers the total energy and the ferroelectricity is stable. When the cell volume is reduced to 90%, total energy is increased with Ti-displacement and ferroelectricity will disappear. The cell volume effect is also confirmed by comparison of the density of states of Ti and O at different cell volumes.     

The Quest for Single-Source Precursors for BaTiO3 and SrTiO3

The reactions between titanium alkoxides Ti(OR)₄ (R = Et,i Pr) and strontium -diketonates Sr(-dik)₂ (-dik = thd, acac) were investigated. The various Sr-Ti species, Sr₂Ti₂(-dik)₄ (OR)₈, have a 1:1 Sr:Ti stoichiometry and were characterized by elemental analysis, FT-IR and by single-crystal X-ray diffraction for Sr₂Ti₂(₃-OiPr)₂ (-OiPr)₄ (OiPr)₂(thd)₄ (1). The hydrolysis-polycondensation reactions of the various species were investigated and the resulting powders analyzed by light scattering and XRD. While acetone was found to have little influence on the hydrolysis reactions of the Sr-Ti species, polycondensation of Ti(OiPr)₄ in neat acetone offers a trinuclear enolate Ti(₃-O)₂(OCMe=CH₂)₃ (OiPr)₅(iPrOH) (4). Comparisons between the Ba-Ti and Sr-Ti systems are given.     

A Three-Dimensional M3AB-Type Hybrid Organic–Inorganic Antiperovskite Ferroelectric: [C3H7FN]3[SnCl6]Cl

Since the first perovskite CaTiO₃ was discovered in 1839, the development of perovskite has a history of 180 years. The emergence of solar cells (CH₃NH₃)PbI₃ has set off the trend of hybrid organic–inorganic perovskite (HOIP) materials. Since then, various HOIPs have sprung up and been widely used in various material devices. Among them, HOIP ferroelectrics have gained widespread attention. However, antiperovskite, as a twin brother of perovskite, has been neglected although it has similar structure with perovskite. Here, we successfully found that [C₃H₇FN]₃[SnCl₆]Cl has a three-dimensional (3D) antiperovskite structure with the formula M₃AB. Importantly, the compound exhibits obvious ferroelectric properties with an Aizu notation of 622F6 at 391 K. To the best of our knowledge, this is the first 3D hybrid organic–inorganic antiperovskite ferroelectric, which will greatly promote the development of antiperovskite families with more superior physical properties.     

Preparation and dielectric properties of the KBiScNbO6 double perovskite

Ceramic KBiScNbO₆ compound was synthesized for the first time. X‐ray diffraction analysis revealed that at room temperature the samples consist of a mixture of the perovskite and pyrochlore phases. The dominant phase is the perovskite one. This phase can be described as distorted pseudocubic Pm3m structure with unit‐cell parameter a_c = 4.069 Å. Rhombohedral distortion leading the polar R3m phase is assumed to be one of possible structural distortions. Dielectric measurements of the compound under study demonstrated anomalies associated with relaxor ferroelectric behavior (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)