NONSTOICHIOMETRY IN PEROVSKITE-TYPE OXIDE CA1-XCEXMNO3-DELTA AND ITS PROPERTIES IN ALKALINE-SOLUTION

Nonstoichiometry in high conductivity perovskite-type oxide Ca1-xCexMnO3-delta was investigated. At room temperature in air, the 3 - delta value was determined to be 2.91 for CaMnO3-delta, which meant that 82% of manganese was tetravalent. Although the 3 - delta value increased by increasing the cerium content, i.e. by doping of higher valent cation into the calcium site, the quantity of Mn4+ in the sample oxide essentially decreased with increasing x. The oxygen contents change reversibly with temperature in air. Change of oxygen content was also observed on discharging this oxide as the cathode material of a battery in alkaline solution. Surprisingly, the sintered ceramics of this oxide worked as a cathode without mixing with a conductive powder such as graphite. Considering the discharging performance, this oxide may be a candidate for the cathode material of the alkaline battery.