Cationic ordering, relaxation dynamics and polaron hopping in a new double perovskite oxide: BaPrCoTaO 6

The Rietveld refinement method is used to investigate the cationic ordering of a new double perovskite oxide BaPrCoTaO6 (BPCT) synthesized by the solid-state reaction technique. X-ray diffraction pattern of BPCT shows monoclinic phase P21/n (C25h) at room temperature with ordering of the B-cations. The superlattice reflections suggest the existence of simultaneous in-phase and out-of-phase tilting. Scanning electron micrograph shows an average grain size ∼3 μm. The Fourier transform infrared spectra suggest two phonon modes. Impedance spectroscopy is used to investigate the relaxation dynamics and hopping mechanism in the temperature range of 303–523 K and in the frequency range of 0.1 kHz–1 MHz. Experimental electric modulus and electrical impedance data are fitted to the Cole–Cole model. The electrical conductivity data are fitted to Jonscher’s universal power law. The activation energy (Ea) calculated from the Arrhenius plots is found to be ∼0.36 eV which shows polaron hopping in BPCT. Impedance data that have capacitive and resistive components is represented by Nyquist diagram.