| Summary: | In this study, LaFe1−yCoyO3 and La1−xSrxFe0.5Co0.5O3 nano-particles with y = 0.00, 0.25, 0.50, 0.75, and 1.00 and x = 0.00, 0.15, 0.30, 0.45, and 0.60 were prepared using the citrate method. The samples were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and tunneling electron microscopy. Detailed structural analysis of the samples was conducted through refining via the Rietveld method and using the Fullprof program. The structural analysis of LaFe1−yCoyO3 revealed that orthorhombic-toward-rhombohedral phase transition with Co doping and rhombohedral-to-cubic phase transformation took place in La1−xSrxFe0.5Co0.5O3 due to an increase in the Sr content. The electrical conductivity and catalytic activity of La1−xSrxFe1−yCoyO3 were also investigated. The results of the structural analysis of LaFe1−yCoyO3 pointed out to the presence of Co2+, Co3+, Fe3+ and Fe4+ ions that would contribute to the overall oxidation activity of these samples. In addition, substituting the lower ionic radius transition metal would decrease the temperature of the complete CO conversion. The increase in the catalytic activity of the sample y = 0.50 in series of LaFe1−yCoyO3 could be mainly attributed to (i) the presence of Fe3+OFe4+ and Co2+OCo3+ couples, (ii) a rhombohedral structure with higher symmetry, and also (iii) the lower value of activation energy and higher value of σOx/σRed. However, substituting Sr for La could increase the temperature of the CO conversion. LaFe0.5Co0.5O3 exhibited 95% CO conversion at 536 K. Keywords: Nano-particles, Ferrite-cobaltite, X-ray diffraction analysis, Structural phase transition, Electrical conductivity, CO oxidation
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