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La3+, Sm3+, and Gd3+ triple-doped ceria Ce1−x(La1/3Sm1/3Gd1/3)xO2−δ (x = 0.06, 0.12, 0.18, 0.24, and 0.30) materials were synthesized by the sol-gel autocombustion method. The selections of dopants were made by an optimized-average atomic number in accordance with the criteria for optimal-doping in ceria. The higher values of relative-density were achieved above 95% by sintering the samples at 1300 °C. The single-phase cubic-fluorite structures, high-density surface-microstructure with uniformly distributed grains, elemental confirmations, and concentration of oxygen vacancies were confirmed using powder x-ray diffraction, scanning electron microscope with energy dispersive spectroscopy, and micro-Raman spectroscopy. Electrical analysis was carried out by impedance spectroscopy, which confirmed the highest value of total-ionic-conductivity, i.e., 0.0381 S/cm at 600 °C with a minimum activation-energy for the Ce0.82La0.06Sm0.06Gd0.06O2−δ (LSG6) composition. Thermal-expansion analyses confirmed the moderate coefficient of thermal-expansion values for all the compositions and were found to be in good agreement with the recently developed materials. The enhanced total-ionic-conductivity and the moderate coefficient of thermal expansion of LSG6 make it as a potential solid-electrolyte for intermediate temperature-solid oxide fuel cell applications. [ABSTRACT FROM AUTHOR]

Effect of Ga addition on structure, resistivity and magnetoresistance of Ba2Fe1−xGaxMoO6 (x = 0.0, 0.1, 0.25 and 0.3) double perovskite. The sol-gel procedure was used to synthesize Ba2Fe1−xGaxMoO6 double perovskite and consolidated at 1150 °C under Ar/H2 atmosphere. Single phase with cubic crystal structure confirmed for all the samples through X-ray diffraction studies. Variation of grain size behavior on the samples surface has been studied by scanning electron microscopy (SEM). The spectra from energy dispersive X-ray spectroscopy (EDS) showed that all the elements Ba, Fe, Ga, Mo and O are present in the samples and there are no impurities in the materials. Fourier transform infrared spectroscopy (FTIR) spectral analysis of 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 materials are double perovskite phase. Magneto-resistance (MR %) of these samples reduce with the addition of Ga content at room temperature (RT). Whereas, MR% at 5 K exhibits opposite trend to the MR% at RT with the Ga-content. It is found that all samples show semiconductor behavior at 5 K and changes into metallic nature as temperature increases showing a semiconductor-metallic transition. This value is larger for composition x = 0.3 and smaller for parent compound. [ABSTRACT FROM AUTHOR]