Electrical properties and scaling behaviour of rare earth based Ho2CoZrO6 double perovskite ceramics

The Ho2CoZrO6 (HCZ) double perovskite has been prepared in polycrystalline form by solid state reaction technique. The analysis of the X-ray powder diffraction pattern indicates that the crystal structure is monoclinic at room temperature with cell parameters a = 8.1858 +/- 0.0023 angstrom, b = 5.2599 +/- 0.0027 angstrom, c = 7.9874 +/- 0.0031 angstrom and beta = 108.51 +/- 0.021 degrees. The compound shows significant frequency dispersion in its dielectric properties. The Cole-Cole model is used to determine the polydispersive nature of dielectric relaxation. The scaling behaviour of dielectric loss and imaginary electric modulus suggest that the relaxation describe same mechanism at various temperatures. Impedance data presented in the Nyquist plot (Z" versus Z') are used to identify an equivalent circuit and to know the bulk and interface contributions. The complex impedance analysis of HCZ exhibits the appearance of both the grain and the grain-boundary contribution. The frequency dependent conductivity spectra follow the universal power law. The magnitude of the activation energy indicates that the carrier transport is due to the hopping conduction. (C) 2012 Elsevier Ltd. All rights reserved.