Structural Characterization of YMexMn1−xO3 (Me=Cu, Ni, Co) Perovskites

Abstract

The structural properties of the YMexMn1−xO3 (Me=Cu, Ni, Co) pseudobinary oxides have been studied by X-ray diffraction and electrical measurements. The powders were prepared by solid state reaction between the corresponding oxides. The incorporation in solid solution of small divalent cations, Cu2+, Ni2+, and Co2+, substituting for Mn in the hexagonal YMnO3 compound, leads to a phase transition in which a perovskite-type structure is formed. The amount of substituting cation necessary for such a transition depends on the cation nature and, to a small extent, on the ionic radius. The phase transition depends strongly on the progressive substitution of the Jahn–Teller Mn3+ cation and therefore of the cooperative Jahn–Teller interaction weakness. The steric influence plays a secondary role, as is shown by the very small variation of the tolerance factor, t, as a function of the cation content. The solid solutions with perovskite-type structure show semiconducting behavior. The conductivity mechanism is of a thermally activated small polaron hopping.