The phenomenon of the incorporation of hydrogen into a single crystal of a-alumina nominally doped with 0.2 mol% CaO was studied by an IR absorption analysis and electrical conductivity measurement in the temperature range of 1073-1673 K. An IR wide band absorption was observed. This band was attributed to the stretching vibration of the OH bond. The H+/D+-isotope effect on the conductivity was observed. It was found that the proton was the dominant charge carrier in the calcium-doped alpha-alumina under a reducing atmosphere containing hydrogen. The chemical diffusion coefficient of the H+/D+ diffusion pair was determined by the relaxation time of the change in the ohmic resistance upon exchanging the atmosphere from H-2 to D-2. The amount of dissolved hydrogen was evaluated to be (3.8 +/- 2.7)x 10(-6) mol(H)/cm(3) using the determined chemical diffusion coefficient and the value of the total conductivity. (C) 2009 Elsevier B.V. All rights reserved.