Depolarization field effect on elasticity of unpoled piezoelectric ceramics

Multiple poling steps and complex electrode configurations are indispensable for high-performance state-of-the-art piezoelectric devices, yet those create partially poled or utterly unpoled regions that significantly change behaviors of piezoelectric devices. Several studies have dealt with method to obtain elastic compliance, yet little attention has been paid to method to obtain elastic loss. Furthermore, physical mechanism to explain the behavior of unpoled piezoelectric ceramic is missing. In this study, we experimentally obtain both effective elastic compliance and elastic loss of unpoled piezoelectric ceramics, using recently developed method called partial electrode (PE), and propose physical mechanism to explain the elasticity. The derivation process for analytical admittance equation for PE is explained and verified with finite element analysis (FEA) simulation. The complex elastic compliance was determined by fitting experimental admittance curve with derived analytical solutions. With the aid of intensive and extensive elastic compliances and elastic losses, we concluded that elasticity of unpoled piezoelectric material lies in between intensive-ness and extensive-ness. We explained this “elastic intermediacy” with depolarization field effect, which is one of the most important phenomena in piezoelectricity.