A temperature-dependent two-step domain-switching model for ferroelectric materials

Piezoelectric stack actuators are promising candidates for use in fuel injection technology. Experimental results for stack actuators have shown that a significant amount of heat is generated when they are driven under high electric-field magnitudes and/or high frequency, both of which occur in fuel injectors. They also exhibit hysteretic nonlinear behavior when driven under high electric-field magnitudes. In this paper, a new domain-switching model for PZT materials is developed. The model is based on changes in potential energy, and accounts for the temperature effect on domain switching. It also accounts for full thermo-electro-mechanical coupling. Additionally, different energy levels are assumed for different domain-switching types. It is assumed that 180° switching is a two-step process caused by two 90° switchings. A finite element implementation of a thermopiezoelectric continuum based on the proposed switching model is presented. The model shows good agreement with experimental results at different temperatures and loading conditions.