The incorporation of H into a single crystal of Mg-doped α-alumina grown by the Verneuil method was studied by using IR absorption and conductivity measurements. In the as-grown sample, a large wide band of IR absorption was observed at 2500 to 3500/cm. This band was attributed to the stretching vibration of the OH bond formed by the incorporated H and host oxide ion. Reversible dissolution of H was confirmed by equilibrium in an H-containing atmosphere. The equilibrium amount of H evaluated by the integral absorbance for the specimen annealed in x%H2O–1%H2–Ar was proportional to the half power of the partial pressure of water. The chemical diffusion of H was determined from the relaxation time of the dissolution phenomenon. The transport number of the proton roughly estimated from the H/D isotope effect observed in the electric conductivity showed that the proton was the major charge carrier in the specimenequilibrated with the gas mixture 20%H2O–1%H2–Ar at 1373K. The anisotropy observed in the IR absorption was found to be due to the fact that H enters between the neighboring O–O pair with a specific spacing and made a H bond with them. Based on the experiment using polarized light, it was concluded that, among 4 kinds of O–O pairs with the different oxide ion octahedron spacings, 2 having a large angle to the basal plane were preferred for the site of H. The anisotropy observed in the chemical diffusion coefficient of H and in the electrical conductivity were reasonably explained based upon the above configuration of the incorporated H.

Incorporation of Hydrogen into Magnesium-Doped α-Alumina. N.Fukatsu, N.Kurita, Y.Oka, S.Yamamoto: Solid State Ionics, 2003, 162-163, 147-59