PMN铁电陶瓷B位有序与介电弛豫特性研究

Relationship Between Dielectric Relaxation Behavior and B-site Ordering of Lead Magnesium Niobate Ferroelectric Ceramics

本文采用退火热处理及掺入La3+离子两种方法，利用高分辨透射电镜、选区电子衍射、X射线衍射等技术对B位离子有序结构与介电弛豫性能的关系进行分析．研究表明，B位离子有序化是直接提高弥散相变（DPT）程度的原因，其机理是离子扩散，存在扩散平衡．退火仅能提高有序度，无法改变有序区尺寸；通过La3+离子掺杂，可有效提高有序区域大小，由于是非化学计量比，造成Nb5+离子在无序区中过度富集，形成焦绿石相．

The mechanism of the B-site ordering and disordering in Lead Magnesium Niobate (PMN)was examined by using both heat treatment and La-doped methods. The B--site structural orderingcharacteristics were exposed by X-ray diffraction (XRD), selected area electron diffraction (SAED)and high-resolution electron microscopy (HREM). The reason of the pyrochlore phase presentingwith the La-doped increased was studied. Based on the analysis of dielectric properties, theincrease in the degree of diffuse phase transition (DPT) in annealed and La-doped PMN observedwas interpreted as the Mg2+:Nb5+ = 1: 1 nonstoichiometric short-range ordered domain accompaniedwith the segregation of the Nb5+ in the disordered area. Furthermore, it was demonstrated thatthe kinetic mechanism of the ordering micro-domain growing was ion diffusion equilibrium by theeffects of the heat treatment on DPT properties of the various amounts of La-doped.