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Ionic Conductivity and Magnesium Vacancy Mobility in Magnesium Oxide

1980; Wiley; Volume: 63; Issue: 11-12 Linguagem: Inglês

10.1111/j.1151-2916.1980.tb09857.x

1551-2916

D. R. SEMPOLINSKI, W. D. Kingery,

Thermal Expansion and Ionic Conductivity

The dc conductivity and ionic transference number of MgO single crystals doped with Al, Fe, and Sc were measured as a function of temperature (1200° to 1600°C) and oxygen pressure (10 −1 to 10 −13 MPa). Magnesium oxide is a mixed conductor with its ionic component directly proportional to the trivalent solute concentration. The activation energy for ionic conduction equals 202 kj/mol and is independent of the specific trivalent solute used. This behavior results from a defect structure for a single trivalent solute for which the charge balance condition is 2[ V Mg '] =[ I Mg ], where [ V Mg ”] is the Mg vacancy concentration and [ I Mg ] the trivalent solute concentration. At lower temperatures and high Sc concentrations, effects attributed to Sc ionvacancy association are observed. Ionic conduction results from Mg vacancy motion with a diffusion coefficient of V Mg ' given by image Deduced values of the Mg‐ion diffusion coefficient lead to the conclusion that the scatter in the published D Mg data largely results from differences in impurity content.