Diffusion of tritons, deuterons, and protons inLiNbO3crystals

Infrared absorption of ${\mathrm{OT}}^{\mathrm{-}}$, ${\mathrm{OD}}^{\mathrm{-}}$, and ${\mathrm{OH}}^{\mathrm{-}}$ ions is used to monitor the presence of the three hydrogenic isotopes in ${\mathrm{LiNbO}}_3$ single crystals. Tritium ions were produced by transmutation of the ${}_3{}^6{}_{}{}^{}\mathrm{Li}$ nucleus via a ${(}_0^1$n${,}_2^4$He) reaction using thermal neutrons. ${\mathrm{OD}}^{\mathrm{-}}$ ions were added to the crystal by subsequent heat treatments in ${\mathrm{D}}_2$O vapor. There exist several configurations for each isotope, and each configuration is common to all three isotopes. Following isochronal heat treatments, the corresponding infrared bands for the three isotopes exhibit similar decay and growth behavior. Diffusion coefficients for all three hydrogenic species have been obtained. Between 900 and 975 K the diffusion coefficients were of the order of ${10}^{\mathrm{-}7}$ ${\mathrm{cm}}^2$/s.