New perovskite related-compounds of Ru(V) in K2NiF4 type structure

The preparation of the new K2NiF4-type compounds, Sr2Co0.5Ru0.5O4, Sr2Ni0.5Ru0.5O4 and Sr2Ga0.5Ru0.5O4 by direct solid state synthesis and the subsequent characterization by powder X-ray diffraction measurements are described. From Rietveld refinements, we found that the compounds have a K2NiF4-type structure with the symmetry of space group I4/mmm. It was found that in these compounds, the substituted trivalent metal ions (M=Co, Ni, and Ga) and the Ru ions are disordered over the octahedral B sites of the K2NiF4 structure. The octahedral Ru–O environment is less elongated in the apical direction in these compounds than in the Sr2RuO4 compound. We also found that the octahedron in Sr2Ga0.5Ru0.5O4 is more symmetric than that of Sr2Co0.5Ru0.5O4 and Sr2Ni0.5Ru0.5O4. The Ru K-edge X-ray absorption measurements showed that Ru ions were in a pentavalent oxidation state.