Dielectric relaxation in perovskite BaAl1 / 2 Nb1 / 2 O3

Abstract

The complex perovskite oxide barium aluminium niobate, BaAl1/2Nb1/2O3 (BAN) is synthesized by a solid-state reaction technique for the first time. The X-ray diffraction of the sample at room temperature shows a monoclinic phase. The field dependence of dielectric response and the loss tangent of the sample are measured in a frequency range from 50 Hz to 2 MHz and in a temperature range from room temperature to 623 K. An analysis of the real and imaginary parts of impedance is performed, assuming a distribution of relaxation times as confirmed by Cole-Cole plot as well as the scaling behaviour of the imaginary part of impedance spectra. This suggests that the distribution of relaxation times is temperature independent. The frequency-dependent maxima in the imaginary impedance are found to obey an Arrhenius law with an activation energy similar or equal to 0.49 eV. The frequency-dependent electrical data are also analysed in the framework of conductivity and electric modulus formalisms. The scaling behaviour of imaginary electric modulus shows the temperature-independent nature of the relaxation time. All these formalisms provided for qualitative similarities in the relaxation time.