Structure and cation distribution in perovskites with small cations at the A site: the case of ScCoO(3)

We synthesize ScCoO(3) perovskite and its solid solutions, ScCo(1−x)Fe(x)O(3) and ScCo(1−x)Cr(x)O(3), under high pressure (6 GPa) and high temperature (1570 K) conditions. We find noticeable shifts from the stoichiometric compositions, expressed as (Sc(1−x)M(x))MO(3) with x = 0.05–0.11 and M = Co, (Co, Fe) and (Co, Cr). The crystal structure of (Sc(0.95)Co(0.05))CoO(3) is refined using synchrotron x-ray powder diffraction data: space group Pnma (No. 62), Z = 4 and lattice parameters a = 5.26766(1) Å, b = 7.14027(2) Å and c = 4.92231(1) Å. (Sc(0.95)Co(0.05))CoO(3) crystallizes in the GdFeO(3)-type structure similar to other members of the perovskite cobaltite family, ACoO(3) (A(3+) = Y and Pr-Lu). There is evidence that (Sc(0.95)Co(0.05))CoO(3) has non-magnetic low-spin Co(3+) ions at the B site and paramagnetic high-spin Co(3+) ions at the A site. In the iron-doped samples (Sc(1−x)M(x))MO(3) with M = (Co, Fe), Fe(3+) ions have a strong preference to occupy the A site of such perovskites at small doping levels.