Preparation of perovskite-type oxide, LaFeO3, by low-temperature decomposition of heteronuclear coordination polymer, (NH4)La[Fe(CN)6]·4.5H2O

摘要

Thermal decomposition of the coordination polymer, (NH₄)La[FeII(CN)₆]·4.5H₂O, with a three-dimensional network structure formed by the FeII–CN–LaIII linkages, was investigated. The decomposition began at around 323 K and proceeded via a few steps to give the anhydride complex, (NH₄)La[FeII(CN)₆], at around 523 K. Further heating gave rise to an abrupt collapse of cyanide groups at around 573 K, followed by the initial formation of the perovskite-type oxide, LaFeO₃, at 603 K and the completion of the decomposition to produce LaFeO₃ at around 898 K. Any formation of the component metal oxides, La₂O₃ and Fe₂O₃, was not recognized during the decomposition. From the XRD line broadening using Scherrer’s equation, the average size of the thermal decomposition product was evaluated to be 21, 22, 25 and 30 nm at 773, 823, 898 and 1073 K, respectively. The specific surface area of the LaFeO₃ particles prepared at 898, 1073 and 1273 K was 13.2, 8.6 and 2.5 m2 g?1, respectively.