Synthesis and thermal decomposition of lanthanide hexacyanochromate(III) complexes, Ln[Cr(CN)₆]·nH₂O (Ln=La−Lu; n=3, 4)

Author： Seto Y. Umemoto K. Arii T. Masuda Y.

ISSN： 1388-6150

Source： Journal of Thermal Analysis and Calorimetry, Vol.76, Iss.1, 2004-04, pp. : 165-177

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Abstract

A series of lanthanide hexacyanochromate(III) n-hydrates, Ln[Cr(CN)₆]·nH₂O (Ln=La−Lu; n=3, 4) were synthesized as the precursors to obtain the homogeneous perovskite-type oxides, LnCrO₃. In the series of the hydrate complexes, Nd[Cr(CN)₆]·4H₂O was the boundary between tetrahydrates and trihydrates, i.e. La, Ce, Pr and Nd formed tetrahydrates, and the other lanthanides formed trihydrates.The crystal structures of La[Cr(CN)₆]·4H₂O and Sm[Cr(CN)₆]·3H₂O were determined by means of the Rietveld analysis of their powder X-ray diffraction profiles. La[Cr(CN)₆]·4H₂O was orthorhombic system, Cmcm, and Sm[Cr(CN)₆]·3H₂O was monoclinic system, P2₁/m.The thermal decomposition of the series complex, Ln[Cr(CN)₆]·nH₂O was followed by means of thermal analyses, powder X-ray diffraction of the solid residue and the mass spectrum of the gaseous products. The homogeneous perovskite-type oxides, LnCrO₃ except of CeCrO₃ were obtained as the final products of the thermal decompositions. The perovskite oxides for La, Pr, Nd and Sm were formed at 800°C, for Eu, Gd, Tb and Dy at 1000°C, and for the other lanthanides at 1100°C. The final product of the thermal decomposition of Ce[Cr(CN)₆]·4H₂O was the mixture of CeO₂ and Cr₂O₃.