Crystal structure and methane oxidation on perovskite-type (La_1−xNd_x)CoO₃ synthesized using citric acid

摘要

Perovskite-type (La_1−x Nd _x )CoO₃ was synthesized using citric acid at 700 °C. The Rietveld method indicated that the crystal structure changed from a rhombohedral to an orthorhombic system at x = 0.4. The Co–O distance of the rhombohedral structure connected continuously with the average Co–O(2) distance of the orthorhombic structure, and the Co–O–Co angle of the rhombohedral structure and the Co–O(2)–Co angle of the orthorhombic structure were continuous. The average particle size of the samples was approximately 55 nm. CH₄ oxidation started above 300 °C, and the temperature corresponding to the 50% conversion (T _1/2) of CH₄ increased linearly with increases in x. It is considered that the amount of adsorbed oxygen decreased in response to the steric hindrance, and that T _1/2 increased as a result.