Predictions of tensile creep behavior of a PZT wafer by a normally distributed free energy model

A constitutive model consisting of Gibbs free energy with normal distribution and an evolution law of phase fraction with critical driving force is proposed to predict the tensile creep behavior of a poled PZT wafer measured by Kim and Lee (2009). From the normal distribution assumption of free energy, the driving force for domain switching between two energy wells becomes dependent on the phase fractions of the variants in the energy wells. Combining the phase fraction-dependent driving force with the proposed evolution law, the tensile creep behavior of the PZT wafer is predicted with relative satisfaction. Different creep responses in short and open electrical boundary conditions, including the so-called switching-induced negative Poisson effect, are also predicted and explained by the effects of an internal electric field generated in open circuit condition on elastic constants and switching mechanism.