The diffusion of 54Mn in Mn1−δO single crystals was measured by using a serial sectioning technique at 1000 to 1500C for deviations from stoichiometry of 0.00003 to 0.12 (table 141). The value of m, in the expression,

D = DoPO21/m

varied from about 6 at low PO2 at all temperatures, to a value approacing 2 at high PO2 and high temperatures. This suggested that diffusion occurred via doubly-charged vacancies at low PO2, with increasing contributions arising from singly-charged and neutral vacancies as PO2 (and the vacancy concentration) increased. For δ-values near to 0.1, the values of D fell below the values extrapolated from lower defect concentrations. The isotope effect for cation self-diffusion was measured by means of the simultaneous diffusion of 52Mn and 54Mn in Mn1-δO (0.0004 < δ < 0.116) at 1300 and 1500C. The isotope-effect results suggested that diffusion occurred via single non-interacting vacancies at low defect concentrations. The defect-defect interactions became important for δ > 0.01. The defect-defect interactions could involve individual defects or could result in defect clusters.

Cation Self-Diffusion and the Isotope Effect in Mn1-δO. N.L.Peterson, W.K.Chen: Journal of Physics and Chemistry of Solids, 1982, 43[1], 29-38

Table 141

Diffusion of 54Mn in Mn1-δO