Thermodynamics of MnO + CoO and MnO + NiO solid solutions

Abstract

Experimental and theoretical studies on oxide solid solutions are presented. The precision of the e.m.f. measurements reported enables the deviations from regular solution models of both MnO + NiO and MnO + CoO solution to be demonstrated. The heats of mixing measured for the latter solution accord fairly well with the results of lattice energy calculations. For MnO + NiO, however, disagreement is found. We suggest that this may be due to a change in electronic structure of the Mn²⁺ ion on entering the NiO host. Simple estimates of the energetics involved support our proposals.