Electromechanical Properties of Ferroelectric Thin Films under Alternating Mechanical and electrical Loadings

Experimental results on electromechanical properties of lead zirconate titanate ceramic sample under combined alternating mechanical and mechanical loadings as manifested by the strain -electric field, and electric displacement -electric field relations have been numerically simulated using four-state Potts model. The dipole from each of the perovskite cells can be assigned to one of the four possible states. The latter are in turn associated with two ferroelastic strain states. In addition to this ferroelastic strain, there are two more strain contributions: elastic and field-induced ones, respectively. In addition to the dipole-dipole and dipole -electric field interactions, the mechanical energy density, coupling between neighboring strain states, as well as the anisotropic switching effect are considered in the system Hamiltonian. The switching of dipoles and hence the evolution of strain can then be evaluated from the change in system Hamiltonian according to Metropolis algorithm. The experimental result on the enhancements of dielectric and piezoelectric responses when both the alternating compressive stress and electric field are out-of-phase is reproduced by numerical simulation.