Identification of crystalline elastic anisotropy in PZT ceramics from in-situ blocking stress measurements

L Daniel,K G Webber,D A Hall,P J Withers,A King

doi:10.1063/1.4874222

Abstract

High energy x-ray diffraction measurements of lattice strains were performed on a rhombohedral Lead Zirconate Titanate ceramic (PZT 55-45) under combinations of applied electric field and compressive stress. These measurements allow the construction of blocking stress curves for different sets of crystallographic orientations which reflect the single crystal elastic anisotropy. A micro-mechanical interpretation of the results is then proposed. Assuming cubic symmetry for the crystalline elastic stiffness tensor and isotropy for the macroscopic elastic properties, the elastic properties of the single crystal are extracted from the measured data. An anisotropy ratio close to 0.3 is found (compared to 1 for isotropic materials). The high level of anisotropy found in this work suggests that crystalline elastic anisotropy should not be neglected in the modelling of ferroelectric materials.

Highlights

Piezoelectric ceramics are widely used as the basis for electromechanical sensors and actuators for control, medical, electronic, and micro-electromechanical systems (MEMS) applications
High energy x-ray diffraction measurements of lattice strains were performed on a rhombohedral Lead Zirconate Titanate ceramic (PZT 55-45) under combinations of applied electric field and compressive stress
The high level of anisotropy found in this work suggests that crystalline elastic anisotropy should not be neglected in the modelling of ferroelectric materials

Summary

Introduction

Piezoelectric ceramics are widely used as the basis for electromechanical sensors and actuators for control, medical, electronic, and micro-electromechanical systems (MEMS) applications. Piezoelectric ceramic materials are subject to relatively high levels of applied electric field and/or mechanical stress, which introduce significant nonlinearity into the dielectric, elastic, and piezoelectric relationships; this nonlinearity arises as a result of ferroelectric and ferroelastic domain switching.. The macroscopic strain under a given set of external loading conditions can be understood as being due to a complex combination of the intrinsic piezoelectric effect, the extrinsic effects resulting from non-180 domain switching, and the development of internal inter-granular stresses. With such complex mechanisms underlying their macroscopic behaviour, ferroelectric materials can neither be described using simple models nor can they be fully understood on the basis of macroscopic measurements alone Some materials can undergo phase switching. With such complex mechanisms underlying their macroscopic behaviour, ferroelectric materials can neither be described using simple models nor can they be fully understood on the basis of macroscopic measurements alone

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