Cation Diffusion in Cr[sub 2]O[sub 3]

Abstract

On employing a sectioning technique with Cr51 as the tracer, the diffusionof Cr ions in nitrogen‐equilibrated Formula was determined from 1045°to 1550°C. Volume diffusion coefficients in hot‐pressed compactsof three different impurity levels conform to the expression Formula. Additions of Formula and Formula do not cause a significant change.Use of lower density sintered compacts provides erroneous results.Conductivity measurements were performed in nitrogen, argon, andair over a wide temperature range; no dependence on oxygen partialpressure was observed. Calculated cation transference numbers varyfrom 10−3 to 10−6. Postulating a simplified model for the defectstructure of Formula , the activation enthalpy for hole motion is8.4 kcal mole−1; the enthalpy of defect formation is 91 kcal mole−1;the activation enthalpy for cation motion is about 31 kcal mole−1.