Electronic structure and electrical properties of Ba2LaTaO6

Ba2LaTaO6 (BLT) ceramic is synthesized by solid state reaction technique. The Rietveld refinement of the X-ray diffraction pattern shows the monoclinic I2/m symmetry of the system. The X-ray photo-emission spectroscopy (XPS) is used to obtain the oxidation states of the constituent ions of BLT. The band gap energy of BLT obtained from UV-visible spectrum is found to be 2.03 eV. Raman spectroscopy is applied to analyze the crystal structure and the vibrational modes of BLT. The density functional theory calculations implemented in Vienna ab initio simulation package with generalized gradient approximation are performed to obtain the density of states (DOS) and the eigen vectors and the eigen frequencies of vibrational modes. The calculated vibrational modes are compared with the experimental Raman modes. The calculated DOS spectrum is compared with the valence band XPS spectrum. The dielectric relaxation of the sample is investigated in the frequency range from 50 Hz to 1 MHz and in the temperature range from 30 °C to 300 °C using alternating current impedance spectroscopy. The relaxation mechanism is explained by fitting the experimental dielectric data with the Cole-Cole model. The frequency dependent ac conductivity spectra are found to follow the power law.