Dielectric properties of rare earth double perovskite oxide Sr2CeSbO6

A polycrystalline rare earth double perovskite oxide, strontium cerium antimonate, Sr2CeSbO6 (SCS), is synthesized by solid-state reaction technique. The X-ray diffraction pattern at room temperature of SCS shows orthorhombic phase with the lattice parameters, a = 8.84 angstrom, b=6.22 angstrom, and c=5.83 angstrom. Fourier transform infrared spectrum shows two phonon modes of the sample at around 550 cm(-1) and 670 cm(-1) due to the antisymmetric SbO6 stretching vibration. The compound shows significant frequency dispersion in its dielectric properties. The complex impedance plane plots show that the relaxation (conduction) mechanism in SCS is purely a bulk effect arising from the semiconductive grains having the grain resistance = 3.8 x 10(6) Omega and the grain capacitance = 1.03 x 10(-10) F at 603 K. The frequency-dependent conductivity spectra follow the universal power law. The conductivity at 100 Hz varies from 2 x 10(-7) Sm-1 to 1.97 x 10(-5) Sm-1 with the increase of temperature from 303 K to 703 K. respectively. The relaxation mechanism of the sample in the framework of electric modulus formalism is modelled by Davidson-Cole equation. The activation energy of the sample, calculated from both conductivity and modulus spectra is found to be similar to 0.15 eV. Such a value of activation energy indicates that the conduction mechanism for SCS is due to electron hopping. The scaling behaviour of imaginary electric modulus suggests that the relaxation describes the same mechanism at various temperatures. (C) 2009 Elsevier Masson SAS. All rights reserved.