Preparation of Perovskite-Type Oxides by the Thermal Decomposition of Heteronuclear Complexes, Ln[Fe_xCo_1-x(CN)₆]⋅4H₂O (Ln=Pr-Yb)

Abstract

Heteronuclear complexes of Ln[Fe_xCo_1-x(CN)₆]⋅4H₂O (Ln=Pr-Yb) were synthesized and their thermal decomposition products were investigated. Thermal decomposition of the complexes results in the formation of perovskite-type oxides for Ln=Pr-Gd even at 800°C. The lattice parameters, a-, b- and c-lattice constants (crystal system: orthorhombic) increase linearly with the ratio of Fe/Co for the perovskite-type oxide. For Ln=Dy through Yb, the Ln₂O₃ phase is observed as the major product for x=0, but its content decreased with an increase in the Fe content; however, a single phase of the perovskite-type oxide was not formed for x=1. The perovskite-type structure for the Fe systems is easier to form compared with the Co systems. We clarified that the formation of the perovskite-type oxide is mainly affected by the ionic radius of the Ln³⁺ ion and the T³⁺ ion (T=Fe or Co).