Dielectric relaxation behaviour of Sr2SbMnO6 ceramics fabricated from nanocrystalline powders prepared by molten salt synthesis

Double perovskite polycrystalline single phase and dense Sr2SbMnO6 (SSM) ceramics, fabricated using the nanocrystalline powders synthesized by molten salt method, exhibited high dielectric constant with low dielectric loss as compared to that of SSM ceramics obtained from the powders prepared by solid-state synthesis method. The dielectric data obtained over a wide frequency (100 Hz-1 MHz) and temperature (190 K-300 K) ranges exhibited distinct relaxations owing to both the grain and grain boundary. The dielectric dispersion was modeled using the Cole-Cole equation consisting of two separate relaxation terms corresponding to the grain and grain boundary. The grain and grain boundary relaxations observed in the Nyquist plots (Z' and Z '') were modeled by an equivalent circuit consisting of two parallel RC circuits connected in series with each other. A careful analysis of both the impedance (Z '' vs.) and modulus (M '' vs omega) behaviour corroborated the conclusions drawn from the dielectric data.