Self-diffusion in α-Al₂O₃ I. Aluminium diffusion in single crystals

Abstract

Aluminium self-diffusion has been measured in single crystals of α-Al₂O₃ in the temperature range 1540–1697°C using ²⁶Al as a radioactive tracer. Two diffusion mechanisms are involved: a lattice diffusion mechanism and a subboundary mechanism. Lattice and subboundary diffusion coefficients obey equations

and

respectively. The results show that lattice diffusion coefficients of aluminium are much lower than those determined earlier. The comparison with oxygen diffusion determined by other workers for the same specimens shows that oxygen and aluminium diffusion coefficients are of the same order of magnitude in the lattice but that aluminium diffusion coefficients are greater than oxygen diffusion coefficients in subboundaries.