Transformation of crystalline heteronuclear cyano complex to crystalline perovskite-type oxide by thermal decomposition

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]·4H2O precursor was elucidated. It was found that the specific surface area of SmFeO3 decreased monotonously with increasing calcination temperature of Sm[Fe(CN)6]·4H2O, while the highest catalytic activity for CO oxidation was achieved for Sm[Fe(CN)6]·4H2O calcined at 600 °C. The size of Sm[Fe(CN)6]·4H2O precursor depended on the molar concentration of starting materials, Sm(NO3)3·6H2O and K3Fe(CN)6, in aqueous solution (Cs); the size of Sm[Fe(CN)6]·4H2O decreased with decreasing Cs. 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.

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► Cyano complex was transformed into perovskite-type oxide by thermal treatment at ca. 600 °C.
► The shape and the size of cyano complex particle were dependent on the concentration of aqueous solution of starting materials.
► The small particle of cyano complex provided that of perovskite-type oxide by thermal treatment, exhibiting a high surface area and a high catalytic activity.