The phenomenon of the incorporation of hydrogen into a single crystal of 0.1 mol% Ba-doped α-alumina was studied using IR absorption analysis. A large wide band of IR absorption was observed. This band was attributed to the stretching vibration of the OH bond. The electrical conductivity of the specimens has been measured by the two-probe ac technique in the temperature range 1073-1673K. The H/D-isotope effect on the conductivity was observed. It was found that the dominant charge carrier of barium doped α -alumina is proton under the reducing atmosphere containing hydrogen.