Loading rate independence of the evolutions of remnant state variables and linear material properties in ferroelectric ceramics during ferroelastic switching

Two series of compressive stress cycles are applied to a commercial poled ferroelectric cube specimen at room temperature 20∘C: one is big stress cycles of increasing magnitude and the other small stress cycles of constant magnitude. The former is applied at five different rates to induce domain switching, and the latter at the fastest loading rate possible to estimate the evolutions of linear material properties during switching. From measured data, we find that the relationships among remnant polarization, longitudinal remnant strain, and transverse remnant strain are equal and the same independent of loading rates. The dependence of piezoelectric coefficient, elastic compliance coefficients, and Poisson’s ratio on remnant state variables is also the same independent of loading rate. These observations lead to conclude that switching processes by compressive stress are loading rate independent, which would be useful in developing constitutive equations for nonlinear behavior of ferroelectric ceramics.