Synthesis and Electromechanical Behavior of "Smart" Ferroelectric Ceramics

9522504 Singh拟议研究的目的是研究循环电场的性质和幅度对裂纹扩展的影响。大多数压电钛酸铅(PZT)材料是在交流电场作用下使用的，机械和电气的联合加载会导致元件失效。本项目中开发的有限元模型将扩展到描述各种边界条件下的PZT的机电响应。此外，一种新的激光拉曼光谱(LRS)技术将被应用于直接测量外加电场产生的裂纹尖端应力分布。计算结果将与使用有限元模型计算的应力进行比较。通过对PZT陶瓷在静电场(DC)和交流电场(AC)作用下的裂纹扩展进行原位研究，利用激光拉曼散射(LRS)直接测量电产生的裂纹尖端应力，建立描述外加电场对裂纹扩展影响的有限元模型，以及研究微观结构和成分对PZT陶瓷诱导相变的影响，将实现所提出的研究目标。%这些研究将使人们对压电材料在电和机械联合载荷作用下的机电响应有一个新的、基本的理解。提出了一种利用激光拉曼散射直接测量裂纹尖端应力的新技术，以及在掺锶PZT系统中诱发相变的可能性。***

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. ***