Dielectric relaxation and conduction mechanism in Ba2GdTaO6

The double perovskite oxide barium gadolinium tantalate, Ba2GdTaO6 (BGT) is synthesized by solid-state reaction technique. The Rietveld refinement of the X-ray diffraction pattern of the sample shows cubic phase at room temperature. Fourier transform infrared (FTIR) spectrum shows two primary phonon modes of the sample at around 587 cm−1 and 858 cm−1. Raman spectrum of the sample taken at 488 nm excitation wavelength, shows three primary strong peaks at 832, 384 and 106 cm−1. Group theoretical study is performed to assign the different vibrational modes of BGT. Dielectric spectroscopy is applied to investigate the ac electrical conductivity of BGT in a temperature range from 333 K to 673 K and in a frequency range of 42 Hz–1 MHz. The complex impedance plane plots show that the relaxation (conduction) mechanism in this material is purely a bulk effect arising from the semiconductive grains. The relaxation time corresponding to dielectric loss is found to obey Arrhenius law with an activation energy of 0.32 eV. The electric modulus formalism is adopted to interpret the relaxation mechanism of BGT.

► Ba2GdTaO6 ceramic is crystallized in cubic structure. ► All Raman and FTIR lines in the experimental spectra are assigned to definite vibrations of the structure. ► Activation energy is 0.32 eV. ► Hopping of charge carriers could be responsible for the dielectric relaxation.