Infra-red absorption measurements were used to characterize OH– and OD– stretching frequencies in Al2O3 crystals both nominally pure and doped with either Ti, V or Mg impurities. Impurities, cooling rates, and ultra-violet irradiation affect the distribution of various OH– (OD–) band intensities. Polarization experiments determined the precise angle of OH– (OD–) ions protruding from the basal plane for several OH– (OD–) bands. Most were <15°, with one at 21°. Diffusion of isotopic species was performed with and without an electric field. Without an electric field, in-diffusion was possible only by exchanging with an existing species. With an electric field, in-diffusion occurred by exchange as well as occupying new sites. Incorporation of H (D) was investigated by subjecting the crystals to a moderate electric field parallel and perpendicular to the crystallographic c-axis at 973 to 1300K in H2O (or D2O) vapor. An initial linear dependence of the percent of exchange with annealing time and applied voltage was observed, indicating that ionic conduction was the dominant mechanism. The activation energy for the H+ ↔ D+ exchange was determined to be about 2.4eV with an electric field of 3000V/cm applied either parallel or perpendicular to the c-axis. The estimated proton (deuteron) mobility was 6 x 10–8cm2/Vs.

Hydrogen-Isotope Transport Induced by an Electric Field in α-Al2O3 Single Crystals. R.Ramírez, I.Colera, R.González, Y.Chen, M.R.Kokta: Physical Review B, 2004, 69[1], 014302 (10pp)