Dielectric behavior and phase transition of perovskite PMN-PT films

The dielectric properties of perovskite relaxor ferroelectrics 0.80Pb(Mg_1/3Nb_2/3)O₃-0.20PbTiO₃ (0.80PMN-0.20PT) thick films fabricated by electrophoretic deposition were investigated as a function of temperature and frequency. The phase transformation of 0.80PMN-0.20PT thick films has two different kinds of phase transition: one is a diffused phase transition around the temperature of dielectric permittivity maxima and the other is a first-order transition from frequency dispersion relaxor ferroelectrics to normal ferroelectrics. The frequency and temperature dependence of the dielectric permittivity maximum was also analyzed to discuss the physical meaning of the Debey, Vogel-Fulcher (V-F) and new-glass (N-G) relations. It is shown that the N-G relation is more suitable to characterize the relaxation behavior than the Debey and V-F relations.