多晶铁电材料的有效电弹性能预报

EFFECTIVE ELECTROELASTIC PROPERTIES OF POLYCRYSTALLINE FERROELECTRIC CERAMICS 1)

本文利用细观力学方法———Ｅｓｈｅｌｂｙ等效夹杂法和ＭｏｒｉＴａｎａｋａ的平均场理论，根据铁电材料的微结构特点，建立了一个细观统计模型对多晶铁电材料的有效电弹性能和模量进行分析预报．在本细观统计模型中，不仅考虑到单晶粒的形状影响，而且考虑铁电畴在外场作用下发生极化转动的影响．

As increasing applications of the ferroelectric ceramics in the field of engineering, how to predict their effective electroelastic properties and improve the reliability of their structure becomes more and more important. As we all know, below the Curie temperature, the ferrolectric ceramics have special microstructure domain and one grain may be composed of many domains. Under the action of external field, the particular domain switching, which has two types of mechanism nucleation and domain wall motion, occurs so that one grain can only contain one domain which polarization is closest to the direction of external electric field. According to these characteristics of ferroelectric ceramics, we established a micro statistical model to describe the process of the domain switching. Further, basing on the Wang's solution for an inclusion in a piezoelectric matrix, we used the methods of micromechanics Eshelby's equivalent inclusion theory and Mori Tanaka's mean field theory to predict and analyze the effective electroelastic properties and moduli of polycrystalline ferroelectric ceramics. This model incorporated the effects of the shape of individual grain and crystallographic domain switching under the action of external field. We took the BaTiO 3 ceramics as example to analyze these effects of domain switching and the shape of individual grain on the effective elcetroelastics properties. These calculated values confirm that 90° domain switching can affect the strain variation but 180° domain switching can not. The model's prediction of the effective electroelastic properties and moduli of BaTiO 3 ceramics is shown to be in agreement with the experimental results.