Diffusion of Hydrogen Isotopes in Pure and Mg-Doped LiNbO3 Crystals

The diffusivity of protons and deuterons is measured parallel to the hexagonal c-axis in pure and Mg-doped LiNbO3 crystals. The infrared absorption of OH− and OD− ions is monitored after isothermal annealing between 450 to 650°C in O2 bubbled through D2O. The activation energy for the out-diffusion of protons and in-diffusion of deuterons is found to be Ep ≈ (1.1 ± 0.2) eV and Ed ≈ (1 ± 0.1) eV, respectively. The proton out-diffusion data are consistent with those obtained from electrical conductivity measurements.