Abstract
The oxygen permeability of non-doped polycrystalline Al2O3 wafers under steep oxygen potential gradients (Δ PO2) was evaluated at temperatures of up to 1973 K. The oxygen permeation occurred by grain boundary (GB) diffusion of oxygen from the higher oxygen partial pressure (PO2) side to the lower PO2 side and by the simultaneous GB diffusion of aluminum in the opposite direction. The exposed Al2O3 was an electronic conductor, and both the aluminum and oxygen ions migrated without any acceleration or inhibition due to the interdiffusion. The ratios of the aluminum and oxygen flux to the oxygen permeation under Δ PO_2 conditions at which mutual GB transport of the ions occurred depended strongly on Δ PO2. The chemical potentials, GB diffusion coefficients, and the flux of aluminum and oxygen were estimated as functions of position in the depth direction of the wafers.
