Crystalline structure and electrical properties of YCuxMn1-xO3 solid solutions

Solid solutions belonging to the Mn-rich region of the YCuxMn1-xO3 system h ave been studied. The powders were prepared by solid-state reaction between the corresponding oxides. Sintered ceramics were obtained by firing at 110 0-1200 degreesC. The incorporation of 30 atomic % Cu to the yttrium mangani te induces the formation of a perovskite-type phase, with orthorhombic symm etry. Increase of the Cu amount do not appreciably affects the orthorhombic ity factor b/a, up to an amount of 50 atomic % Cu. Above this Cu amount, a multiphase system has been observed, with the presence of unreacted Y2O3,YM nO3, Cu2Y2O5 and, the perovskite phase. DC electrical conductivity measurem ents have shown a semiconducting behavior for all the solid solutions with perovskite-type structure. The room temperature conductivity increases with Cu until similar to 33 atomic % Cu, and then decreases. Small polaron hopp ing 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.