Mutual grain-boundary transport of aluminum and oxygen in polycrystalline Al2O3 under oxygen potential gradients at high temperatures

Abstract

The oxygen permeability of non-doped polycrystalline Al2O 3 wafers under steep oxygen potential gradients (δPO 2 ) 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 δPO2 conditions at which mutual GB transport of the ions occurred depended strongly on δPO2. 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. © 2011 The Ceramic Society of Japan.