Infra-red absorption measurements of OD- and OH- ions were used to study the diffusion rates of deuterons and protons in -phase crystals. It was found that the threshold temperature for the in-diffusion of deuterons during isochronal annealing (0.5h) was 1273K. At 1323K, the diffusivity in the c-axis direction was 8 x 10-8cm2/s. The activation energy was equal to about 5eV. It was deduced that the mechanism mainly involved the replacement of protons by deuterons. The application of an electric field (1000V/cm) enhanced the diffusion of deuterons, and the threshold temperature decreased to 1200K. Deuterons could also be introduced without replacing protons. A crystal was chosen in which OH- ions were undetectable. Heat treatment in D2O vapor at temperatures as high as 1800K did not produce OD- ions. However, the application of a field of 1200V/cm at 1373K produced a 2407/cm band. A small amount of OH- which was present after heat treatment was attributed to contamination, or to trace amounts of H2O in the D2O. The 2438/cm band grew disproportionately faster after this treatment, and it was suggested that, under the influence of the electric field, deuterons could be incorporated without any exchange mechanism. Luminescence experiments were carried out in order to detect Ti3+ emissions before and after applying an electric field. The results suggested that the charge compensator which permitted the incorporation of positively charged deuterons was the Ti3+ ion. The intensity of the Ti3+ emission was much weaker after deuterons had been diffused into the crystal; thus indicating that these ions were probably reduced to Ti2+.

R.Ramírez, R.González, I.Colera, Y.Chen: Materials Science Forum, 1997, 239-241, 395-8