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Double perovskite materials Sr2Fe1 − xInxMoO6 (x = 0.0 and 0.2) were synthesized by sol-gel process. The materials were analyzed by X-ray diffraction and it is found that perovskite material crystallized in tetragonal structure, with space group I4/mmm. Variation of porosity and grain size behavior of samples has been studied by scanning electron microscopy. The spectra from energy dispersive X-ray spectroscopy showed that all the elements Sr, Fe, In, Mo and O are present in the samples and there are no impurities in the materials. Fourier transform infrared spectroscopy spectral analysis of present samples produced three characteristic absorption bands of Mo-O and Fe-O vibrations in the wave number range 400-1000 cm− 1 which confirmed the present material is double perovskite phase. From electron spin resonance spectra, it is found that the value of g ~ 2.00 and indicates that Fe is in 3 + ionic state in these materials. It was found from conductivity results that conductivity of indium doped sample reduced when compared with parent compound Sr2FeMoO6. Indium doped sample showed semiconductor behavior whereas parent sample showed semiconductor-metallic behavior from 5 to 300 K. The electrical conductivity of the materials increases with increase of magnetic field at constant temperatures 5, 150 and 300 K. Magnetoresistance (%) of the present materials increases with magnetic field range from 0 to 4 T and decreases with temperature from 5 to 300 K. Magnetoresistance (%), saturation magnetization and transition temperature of indium doped material has lesser value compare to Sr2FeMoO6. [ABSTRACT FROM AUTHOR]

Double perovskite oxide Ba2CeZrO6 is synthesized by sol–gel technique for the first time. The X-ray diffraction pattern at room temperature show that the sample exists in single phase and crystallizes in cubic structure with space groupFm3-m. The lattice parameter is found to be 0.8635 nm. A scanning electron micrograph image of the Ba2CeZrO6 sample show uniform distribution of grains size ranging from 2.4 to 3 μm. EDAX spectra showed that Ba2CeZrO6 sample contains only Ba, Ce, Zr and O elements which are closer to stoichiometric ratio. Fourier transform infrared spectra of Ba2CeZrO6 showed the peaks observed corresponds to CeO6 and ZrO6 octahedra indicates the formation of double perovskite structure. The tolerance factor (t) of Ba2CeZrO6 sample is 0.90 suggests unit cell has a small distortion from ideal cubic structure. Frequency (100 Hz–5 MHz) dependent impedance spectroscopy studies were carried out at different temperatures ranging from room temperature to 400 °C. The decrease in impedance (Z), relaxation time (τ) and grain, grain boundary resistance and increase in conductivity with increase in temperature shows the semiconducting nature of the Ba2CeZrO6 sample. Nyquist analysis showed the contribution of grain and grain boundary resistances for the relaxation process in Ba2CeZrO6 sample. The relaxation mechanism in the sample is found to be independent of temperature. The activation energy of Ba2CeZrO6 sample is found to be 0.38 eV. [ABSTRACT FROM AUTHOR]