Synthesis and Electromechanical Behavior of "Smart" Ferroelectric Ceramics

本研究的目的是研究循环电场的性质和振幅对裂纹扩展的影响。大多数压电钛酸铅（PZTs）是在交流电场下使用的，在这种情况下，机械和电气的联合载荷会导致元件失效。在当前项目中开发的有限元模型将被扩展到描述PZT在各种边界条件下的机电响应。此外，还将应用激光拉曼光谱（LRS）技术直接测量外加电场作用下裂纹尖端应力的分布。结果将与有限元模型计算的应力进行比较。本文的研究目标将通过对PZT陶瓷在静（直流）和循环（交流）电场下的原位裂纹扩展进行研究，利用LRS直接测量原位产生的裂纹尖端应力，建立一个有限元模型来描述外加电场对裂纹扩展的影响。研究了PZT陶瓷的微观结构和成分对诱导相变的影响。这些研究将导致对压电材料在电和机械联合载荷下的机电响应有一个新的和基本的理解。本文将展示一种利用LRS直接测量裂纹尖端应力的新技术，以及在掺锶PZT体系中诱导相变的可能性。* * *

9522504 Singh The objective of the proposed research is to study the effect of the nature and amplitude of cyclic electric fields on crack propagation. Most piezoelectric leadzirconium titanates (PZTs) are used under AC fields, where the combined mechanical and electrical loading can cause component failure. Finite element models developed in the current project will be extended to describe the electromechanical response of PZT under a variety of boundary conditions. In addition, a novel technique of laser Raman spectroscopy (LRS) will be applied to directly measure the distribution of crack tip stresses produced by applied electric fields. The results will be compared with stresses calculated using FEA models. The proposed research objectives will be accomplished by performing in situ crack propagation studies in PZT ceramics under static (DC) and cyclic (AC) electric fields, directly measuring electricallygenerated crack tip stresses in situ using LRS, developing a finite element model to describe the effect of applied electric field on crack propagation, and studying the influence of microstructure and composition on the induced phase transformations in PZT ceramics. %%% These studies will lead to a new and fundamental understanding of the electromechanical response of piezoelectric materials under combined electric and mechanical loads. A new techniques using LRS for directly measuring crack tip stresses will be demonstrated along with the possibilities of induced phase transformation in the strontium-doped PZT system. ***