Dielectric response and impedance spectroscopy of 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ thin films

Abstract

Dielectric response of 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (PMN-PT) thin films deposited by pulsed laser deposition has been studied as a function of frequency over a wide range of temperatures. The films exhibited maximum frequency dispersion in both real and imaginary part of dielectric susceptibility near and below the dielectric transition temperature. The relaxor behavior in the films was confirmed from the diffused phase transition (DP) together with frequency dependent of transition temperature (T_m). The frequency dependence of transition temperature T_m (temperature of the maximum of dielectric constant) was studied in terms of Vogel-Fulcher relation. The dielectric relaxation of PMN-PT thin films was studied at different temperatures using the complex impedance (Z^∗) and electric modulus (M^∗) formalism. The shape of complex impedance curve inferred that only one type of dielectric relaxation was involved in the present case. This was attributed to the contribution of bulk grain of the films while the other probable sources, such as grain boundaries, film electrode interfaces were negligible. The films exhibited Debye type dielectric relaxation at temperature sufficiently above the temperature of permittivity maximum (T_m), while a multi-Debye relaxation was observed at lower temperatures (<200 ° C), which was confirmed from the broad spectrum of dielectric relaxation. The average relaxation times estimated from Cole-Cole plots varied with temperature according to the V-F relation.