DEFECT STRUCTURE OF MGO CONTAINING TRIVALENT CATION SOLUTES - OXIDATION-REDUCTION BEHAVIOR OF IRON

Association energies for ferric ion magnesium vacancy dimers and trimers derived from shell-model calculations are combined with oxidation-reduction equilibria data in concentrated crystalline solutions to derive equilibrium defect concentrations for relatively dilute solutions. The several simultaneous non-linear equations required are solved with a numerical iteration method. Calculated results are compared with experimental determinations of solute concentration and oxygen pressure. It is found that with a slight reduction of the shell-model energies, the defect model is in good accord with experimental data at temperatures greater than 1300° C. At lower temperatures, agreement is poor and it is surmised that solute-vacancy clusters may be important. © 1979 Chapman and Hall Ltd.