STRUCTURAL CHARACTERIZATION OF THE ORTHORHOMBIC PEROVSKITES - [ARUO3 (A=CA, SR, LA, PR)]

The GdFeO3-type perovskites, ARuO3 (A = Ca, Sr, La, Pr) and their solid solutions have been synthesized and their structures were refined by X-ray Rietveld analysis. In the Sr1-xCa(x)RuO3 system, the twelve A - O bondlengths split in two groups of eight short and four long distances, and the difference between two groups becomes larger with increasing x. The bend in the zig-zag chains formed by the corner-sharing RuO6 octahedra increases with x, while no change in the Ru-O distances was observed. These structural changes correspond to the weakening of the ferromagnetic interactions from x = 0 to 0.6. For the ARuO3 (A = Ca, Sr, La, Pr) series, the distortion from the ideal cubic perovskite increases in the order of Sr, La, Ca, Pr. The splitting of the two groups for the long and short A-O distances and the Ru-O-Ru angle decreases in that order, which corresponds to the metallic property for A = Sr, La, Ca and semiconducting for A = Pr.