Interdiffusion in the System MgO‐MgAl 2 O 4

Interdiffusion coefficients in single‐crystal MgO were determined using an MgO‐MgAl 2 O 4 diffusion couple. For a concentration of 1 mol% Al 2 O 3 in MgO, the interdiffusion coefficient can be expressed as D =2.0±0.2 exp (−76,000±3,000/ RT ) for the MgO‐MgAl 2 O 4 couple. This relation compares well with previous measurements in the MgO‐Al 2 O 3 system. The interdiffusion coefficients, which increased with the mol fraction of cation vacancies, were in the range of 10 −8 to 10 −10 cm 2 s −1 for the concentrations and temperatures studied. Diffusion was enhanced below 1640°C if powdered MgAl 2 O 4 was used. Self‐diffusion coefficients for Al 3+ ions in MgO were calculated; Al 3+ diffuses faster than Cr 3+ in MgO.