Preparation and electrical properties of sintered oxides composed of Mn1.5Co(0.25+X)Ni(1.25-X)O4 ( 0 ≦ X ≦ 0.75) with a cubic spinel structure

Abstract

Monophase cubic spinel-type oxides of Mn1.5Co (0.25+X)Ni(1.25-X)O4 (0 ≦ X ≦ 1) were prepared through the oxidation of specimens sintered at 1400 °C. The oxides with 0 ≦ X ≦ 0.75 composition are focused on in this study, as the oxides with 0.75 < X ≦ 1 composition did not convert into a monophase cubic spinel structure. The electrical conductivity of the sintered bodies was confirmed to increase exponentially with increasing temperature. In the composition range of 0 ≦ X ≦ 0.75, both the electrical conductivity and the Seebeck coefficient increased with increasing X. The oxides with composition between 0 ≦ X < 0.57 were n-type semiconductors, whereas those with 0.57 < X ≦ 0.75 were p-type. It was concluded that electrical conduction in the specimens is controlled by small polaron hopping. © 2007 Springer Science+Business Media, LLC.