The Nature of Piezoelectricity of Ferroelectric SbSI Crystal

The contribution of Sb atoms soft mode to the temperature dependences of the piezoelectric modulus e(T) and atomic equilibrium position's difference Δz(T) has been studied theoretically, when SbSI crystal is deformed along crystallographic x(a), y(b) and z(c)—axes. The largest change of e(T) occurs in the ferrophase near the phase transition (when T ≈ TC ). At T < TC , the e(T) changes become slow. It has been found that value and anomalous temperature dependence of e(T) and Δz(T) is influenced by the change of mean potential energy of Sb atoms in soft mode due to its interaction with phonons.