Nonlinear Dielectric Susceptibility in Pb(Sc1/2Ta1/2)O3 Single Crystals

The third-order nonlinear dielectric susceptibility epsilon(3) induced by the cube of the electric field is investigated in the paraelectric phase of Pb(Sc1/2Ta1/2)O-3 (PST). It is confirmed that epsilon(3) takes a positive value near T-m (approximate to 14 degrees C), at which the linear permittivity shows a maximum value, and becomes negative at 33.4 degrees C, indicating that the ferroelectric phase transition in PST is essentially the first-order phase transition very close to the second-order transition. Our experimental results of the temperature dependences of the linear and nonlinear dielectric susceptibilities are discussed on the basis of the Landau-type free-energy density. A change in the sign of epsilon(3) near the phase transition temperature in the paraelectric phase may be a phenomenon common to many perovskite-type ferroelectrics.