Hydrogen and lithium tracer diffusivities as a function of hydrogen concentration in Li(Nb,Ta)O3 single crystals

For LiNb 1-x Ta x O 3 single crystals, the ion diffusivities of the species Li and H (as an impurity) have strong influence on the overall conductivity at temperatures below 600 °C. We investigated the diffusion of H and Li in LiNbO 3 , LiTaO 3 , and LiNb 0.15 Ta 0.85 O 3 single crystals as a function of H concentration over two order of magnitude at 510 °C. The hydrogen diffusion experiments were realized by isotope exchange of deuterium (D) and hydrogen (H) in a gaseous D 2 O atmosphere and infra-red spectroscopy. The lithium diffusion experiments were done by 6 Li/ 7 Li tracer exchange and Secondary Ion Mass Spectrometry. The diffusivities of both types of species decrease only slightly with increasing hydrogen concentration between 5 × 10 16 cm −3 and 3 × 10 18 cm −3 by a maximum factor of two to three for each type of diffusor. We suggest that the increased incorporation of hydrogen up to a concentration of about 3 × 10 18 cm −3 into the lattice modifies only very slightly the migration of both species.