Nonstoichiometry in perovskite-type oxide Ca_1−x Ce _x MnO_3−δ and its properties in alkaline solution

Abstract

Nonstoichiometry in high conductivity perovskite-type oxide Ca_1-x Ce _x MnO_3-δ was investigated. At room temperature in air, the 3-δ value was determined to be 2.91 for CaMnO_3-δ, which meant that 82% of manganese was tetravalent. Although the 3-δ 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 increasingx. 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.