The Study On The Mechanical Properties Coupled With Electricity Of The Compositionally Graded Material Pb (Zr_1-xTi_x)O₃（PZT）

This dissertation studied the effects of electricity and strain on the mechanical properties coupled with electrical properties of compositionally graded material PbZr1-xTixO3 (PZT) by modeling different models. There are three main topics being included in this dissertation:①studying the relationship among the strain, the remnant polarization and the nonlinear dielectric coefficient by a 3D model; ② simulating the evolution of domain structure of the ferroelectric poly-crystals under the conditions of electricity coupled with strain with phase field method by a 3D poly-crystal model in the real space, simultaneously, the mechanical and electrical properties of the ferroelectric poly-crystals under different conditions has been analyzed qualitatively; ③ studying the effects of compression-anisotropic and isotropic loading, tension-anisotropic and isotropic loading on the polarization vortex and the polarization distribution of the nano-dot. The results suggested that:(1) ①Under compressive strain, the remnant polarization decreases with the decreasing of the strain and the increasing of the tensile strain, but the remnant polarization under compressive strain is larger than that under tensile strain; ②under the same conditions of applied strains, the remnant polarization is the largest when x=0.47;③the dielectric with different composition goes a nonlinear relationship while external strains have been applied. The dielectric increased with the compressive strain decrease while it increased with the tensile strain decrease;(2) The evolution of domain structure indicated that domain switching occurs preferentially both in the grain boundaries with lower orientation difference and the grain’s interior which has a relative higher orientation with respect to the global coordinate. The nucleation and the formation of multi-domain as well as the process of depolarization induced by electric field under a tensile strain are easier than that under a compressive strain. Comparatively, a compressive misfit strain increases the macroscopic coercive field and remnant polarization while a tensile misfit strain decreases both of them. In addition, a compressive strain decreases the non-linear dielectric constant while a tensile strain increases it;(3)①compressive-isotropic loading decreases the number of the polarization vortex and the applied loading decreases the average polarization;②when the applied loading is under the critical value, the number of polarization vortex is fixed under the compressive-anisotropic loading, tensile-anisotropic loading and the tensile-isotropic loading,. The number of the polarization vortex begins increasing with loading larger than critical value and the average polarization is increasing with the increase of the applied loading.