|Author:||Chow, Ching-kin Simon|
|Title:||Simulation of low frequency electromechanical responses of ferroelectric ceramic|
|Subject:||Hong Kong Polytechnic University -- Dissertations.|
|Department:||Department of Applied Physics|
|Pages:||xxx, 146 leaves : ill. ; 30 cm.|
|Abstract:||Perokvskite type ferroelectrics such as lead zirconate titanate (PZT) ceramics have been widely used in electromechanical devices due to their excellent electromechanical coupling effects and high permittivities. However, the underlying physical picture is still unclear. In particular, these materials exhibit a high degree of non-linearity and hysteretic behaviors when it is subject to large signal and low frequency loading. Moreover, the electromechanical properties are sensitive to the loading conditions: both electrical and mechanical. To understand the effects of different loading conditions on these properties and to find out the loading condition for the optimal condition are vitally important. In this work, it is intended to investigate these effects based on several experimental reports. These loading conditions include: (1) static longitudinal compressive stress and alternating electric field, (2) static electric field and alternating compressive stress and (3) both alternating electric field and compressive stress. Numerical simulation based on the two-dimensional four-state Ports model has been performed. The electromechanical behavior is basically achieved by 90o dipolar rotation at the domain wall. Furthermore, these dipoles with four possible orientations are associated with the ferroelastic strain states. The dynamic of these dipole states as well as strain states is governed by a system Hamiltonian which includes the couplings between the neighboring dipoles, the electrical energy density, mechanical energy density, as well as the anisotropic switching effects. The simulation result for each of these loading conditions is compared with experiments and it shows a good agreement.|
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