(The) modeling and effect of residual stress in PZT ceramics

Abstract

Ferroelectric microstructural residual stress model was proposed and the validity of this model was tested by the 90˚ domain width calculation. Microstructrual residual stress effects on the physical properties were studied on the basis of the suggested model in PZT ceramics. The residual stress in a material was changed by the grain size (range of 5 - 30 μm), and poling. The 90˚ domain width calculated from the model was nearly coincident with the measured value within the order of magnitude. The total residual stress increase with decreasing grain size. This fact was confirmed by measuring 1)the dielectric constant difference between heating and cooling, and 2) the enthalpy change during phase transformation. On the other hand the components(tensile and compressive) of the residual stress decrease with decreasing grain size. The inhomogeneous microstructural residual stress distribution due to inhomogeneous grain size distribution was the cause of diffuse characteristic phase transition in small grain size. During poling the microcracks were created by superimposing of the domain reorientation inducing stress on the existing residual stress. The morphology of them were determined by the interaction of induced and residual stresses. After poling the dielectric constant is determined from compromising effects between electrostriction inducing stress and dipole rotation to the poling direction