Origin of fundamental functions in relaxor ferroelectrics

弛豫铁电体具有宽而大的介电极化率和最大的压电响应，是大容量小尺寸电容器、致动器和超声波器件的理想材料。然而，尽管到目前为止已经提出了各种模型，但对于它们巨大的介电响应的起源还不是很清楚。特别是在一些典型的弛豫体，如Pb(Mg1/3Nb2/3)O3中，长程有序化并没有发展到液氦温度。我们认为这一现象对弛豫特性是必不可少的，并用光学、非线性光学和中子散射技术进行了研究。我们之前的研究表明，在外加电场的作用下，可以诱导出长程有序，但如果样品经历不同的史前，则会显示出截然不同的路径。研究表明，长时间孵化后形成的长程有序结构，在低温下可达数十小时以上。发现弛豫过程至少可以分为两个过程：一个是较快的响应，服从德拜型定律；另一个是长过程，如果引入一个起始时间，它可以被归一化。我们现在正在分析这些数据，将弹性长程相互作用力引入金兹堡-朗道方程。

Relaxors ferroelectrics exhibit broad and huge dielectric susceptibility and the biggest piezoelectric response and are promising materials for small-size capacitors with large capacitance, actuators and ultra-sonic devices. However, the origin of their colossal dielectric response is not well understood, although various models have been proposed so far. In particular, in some prototype relaxors such as Pb (Mg1/3Nb2/3)O3, the long-range order is not developed down to liquid helium temperature. We think that this phenomenon is essential for relaxor properties and have investigated by means of optical, nonlinear optical and neutron scattering techniques. Our previous study revealed that the long-range order can be induced under the applied electric field but shows quite different paths if the specimen experiences different pre-history. The present study clarified that the long-range order develops after long incubation time, which overpasses several ten hours in low temperature. The relaxation processes are found to be classified by at least two processes : One is rather fast response which obeys the Debye-type law and the other is the long process which can be normalized if we introduced an onset time. We are now analyzing these data introducing the elastic long-range interaction force into the Ginzburg-Landau equation.