Crystalline structure and electrical properties of YCuxMn1–xO3 solid solutions

Solid solutions belonging to the Mn-rich region of the YCuxMn1–xO3 system have been studied. The powders were prepared by solid-state reaction between the corresponding oxides. Sintered ceramics were obtained by firing at 1100–1325 °C. The incorporation of 30 at.% Cu to the yttrium manganite induces the formation of a perovskite-type phase, with orthorhombic symmetry. Increase of the Cu amount do not appreciably affects the orthorhombicity factor b/a, up to an amount of 50 at.% Cu. Above this Cu amount, a multiphase system has been observed, with the presence of unreacted-Y2O3, YMnO3 and Y2Cu2O5, along with a perovskite phase. DC electrical conductivity measurements have shown a semiconducting behaviour for all the solid solutions with perovskite-type structure. The room temperature conductivity increases with Cu until ∼33 at.% Cu, and then decreases. Thermally activated small polaron hopping mechanism, between Mn3+ and Mn4+ cations, controls the conductivity in these ceramics. Results are discussed as a function of the Mn3+/Mn4+ ratio for each composition.