ELECTRICAL PROPERTIES AND SITE DISTRIBUTION OF CATIONS IN (Mn//yCo//1// minus //y)//0//. //4Fe//2//. //6O//4.

The high-temperature electrical properties (conductivity and thermopower) of the Co//0//. //4Fe//2//. //6O//4-Mn//0//. //4Fe//2//. //6O//4 join were measured in order to determine the cation intersite distribution and establish the conduction mechanism. The cobalt and manganese site occupancies show a nearly linear composition dependence. Trivalent iron occupancies reflect the transition from an octahedral substituent (Co) to a tetrahedral substituent (Mn), but any influence on the iron distribution reaction is minimal.