Department of Physics, Alexandru Ioan Cuza University, 11 Bv. Carol I, 700506 Iasi, Romania.
J Phys Condens Matter. 2011 Aug 17;23(32):325901. doi: 10.1088/0953-8984/23/32/325901. Epub 2011 Jul 25.
The properties induced by the M(4+) addition (M = Zr, Sn, Hf) in BaM(x)Ti(1-x)O(3) solid solutions have been described on the basis of a 2D Ising-like network and Monte Carlo calculations, in which BaMO(3) randomly distributed unit cells were considered as being non-ferroelectric. The polarization versus temperature dependences when increasing the M(4+) concentration (x) showed a continuous reduction of the remanent polarization and of the critical temperature corresponding to the ferroelectric-paraelectric transition and a modification from a first-order to a second-order phase transition with a broad temperature range for which the transition takes place, as commonly reported for relaxors. The model also describes the system's tendency to reduce the polar clusters' average size while increasing their stability in time at higher temperatures above the Curie range, when a ferroelectric-relaxor crossover is induced by increasing the substitution (x). The equilibrium micropolar states during the polarization reversal process while describing the P(E) loops were comparatively monitored for the ferroelectric (x = 0) and relaxor (x = 0.3) states. Polarization reversal in relaxor compositions proceeds by the growth of several nucleated domains (the 'labyrinthine domain pattern') instead of the large scale domain formation typical for the ferroelectric state. The spatial and temporal evolution of the polar clusters in BaM(x)Ti(1-x)O(3) solid solutions at various x has also been described by the correlation length and correlation time. As expected for the ferroelectric-relaxor crossover characterized by a progressive increasing degree of disorder, local fluctuations cause a reducing correlation time when the substitution degree increases, at a given temperature. The correlation time around the Curie temperature increases, reflecting the increasing stability in time of some polar nanoregions in relaxors in comparison with ferroelectrics, which was experimentally proved in various types of relaxors.
基于二维伊辛相似网络和蒙特卡罗计算，描述了 M（4+）（M=Zr、Sn、Hf）添加在 BaM（x）Ti（1-x）O（3）固溶体中引起的特性，其中 BaMO（3）随机分布的单元被认为是非铁电的。随着 M（4+）浓度（x）的增加，极化与温度的关系显示出剩余极化和铁电-顺电相变的临界温度的连续降低，以及从一级相变到二级相变的转变，其转变发生的温度范围较宽，通常被报道为弛豫体。该模型还描述了系统在居里温度以上的高温下，随着时间的推移，通过增加取代（x），减少极性簇平均尺寸并提高其稳定性的趋势。当通过增加取代（x）引起铁电-弛豫体交叉时，在极化反转过程中，平衡微极状态同时描述了 P（E）环。比较监测了铁电（x=0）和弛豫体（x=0.3）状态下极化反转过程中的 P（E）环。弛豫体组成的极化反转是通过多个成核畴的生长（“迷宫状畴模式”）进行的，而不是铁电状态的大尺度畴形成。在不同 x 下的 BaM（x）Ti（1-x）O（3）固溶体中，通过相关长度和相关时间描述了极性簇的时空演变。正如铁电-弛豫体交叉所预期的那样，随着无序程度的逐渐增加，局部波动导致在给定温度下，取代度增加时相关时间减少。在居里温度附近的相关时间增加，反映了在弛豫体中一些极性纳米区域的稳定性随时间的增加，这在各种类型的弛豫体中得到了实验证明。
