The thermal decomposition reaction of crystalline heteronuclear cyano complex precursor to crystalline perovskite-type oxide catalyst was investigated. From X-ray single crystal analysis and XRD, FT-IR, TG-DTA, SEM, and BET measurements, the thermal decomposition process of Sm[Fe(CN)(6)]center dot 4H(2)O precursor was elucidated. It was found that the specific surface area of SmFeO(3) decreased monotonously with increasing calcination temperature of Sm[Fe(CN)(6)]center dot 4H(2)O, while the highest catalytic activity for CO oxidation was achieved for Sm[Fe(CN)(6)]center dot 4H(2)O calcined at 600 degrees C. The size of Sm[Fe(CN)(6)]center dot 4H(2)O precursor depended on the molar concentration of starting materials, Sm(NO(3))(3)center dot 6H(2)O and K(3)Fe(CN)(6), in aqueous solution (C(s)); the size of Sm[Fe(CN)(6)]center dot 4H(2)O decreased with decreasing C(s). The decrease in particle size of cyano complex was found to result in the increase in specific surface area of perovksite-type oxide obtained after calcination. (C) 2011 Elsevier B.V. All rights reserved.