Dielectric Relaxation and Electronic Structure of Double Perovskite Ca2AlNbO6

Abstract

The dielectric property and the electronic structure of calcium aluminium niobate, Ca2AlNbO6 (CAN) synthesized by solid state reaction technique are investigated. The field dependence of dielectric response, loss tangent and conductance is studied in the temperature range from 303 to 443 K and in a frequency range from 50 Hz to 1 MHz. The Cole-Cole model is used to analyze the distribution of relaxation times. The temperature dependence of the most probable relaxation time obtained from imaginary part of dielectric function follows the Arrhenius law with the activation energy of 0.50 eV. The electronic structure of CAN is investigated using the first principles full potential linearized augmented plane wave method. A direct band gap of 3.3 eV is obtained between the top most valence band of O-2p character and the bottom of conduction band of Nb-4d character. The x-ray photoemission spectroscopy (XPS) study of the sample is performed to examine the electronic structure calculation. The calculated density of states is compared with the experimental XPS valence band spectrum.