Sound attenuation in Ba₁_-xCa_xTiO₃ ferroelectric perovskites

Abstract

Theoretical expression of attenuation constant of anharmonic Ba₁_-xCa_xTiO₃ ferroelectric crystal in paraelectric phase using double times temperature dependent Green’s function technique, is derived. The variation of attenuation constant with frequency and temperature has been studied by considering third- and fourth-order anharmonic interactions, taking electric field as an important parameter. The mass and force constant change due to the presence of impurity atoms in Silverman-Joseph Hamiltonian augmented with higher order anharmonic terms. The effect of electric field, defect and anharmonicity on stabilization of the soft mode frequency has also been studied. The attenuation constant increases with increasing temperature and frequency in the presence of an electric field. In the vicinity of the Curie temperature, attenuation constant increases anomalously.