Crystalline structure and electrical properties of YCoxMn1-xO3 solid solutions

Solid solutions corresponding to YCoxMn1-xO3 system with x = 0.2...0.7 have been studied. The powders were prepared by solid state reaction of corresponding oxides. Sintered bodies were obtained firing between 1250 and 1350 degreesC. The incorporation of 25 at.% of Co in the Yttrium manganite induced the appearance of a perovskite-type phase with orthorhombic symmetry and Space Group Pbnm. This feature was extended at least up to an amount of 70 at.% of Co. The increase of the Cc content from 25 to 70 at.% led to a monotonic decrease of the orthorhombicity factor b/a. Electrical measurements have shown a semiconducting behaviour for all solid solutions with the perovskite-type structure. The room temperature conductivity increased with Co until the 33 at.% of Co, and then decreased. The 60/40 Co/Mn composition showed an increase of the electrical conductivity in comparison to the 50/50 composition and a corresponding decrease of the activation energy. Small polaron hopping mechanism is supposed to control the conductivity. (C) 2002 Elsevier Science Ltd. All rights reserved.