The dependence of the diffusion coefficient on the proton concentration in the proton exchange of LiNbO3

The concentration-dependent diffusion coefficient for proton-lithium counter-diffusion is studied in this paper. Depth profiles of the proton concentration for proton-exchanged LiNbO₃ were measured by secondary ion mass spectroscopy (SIMS). The concentration-dependent diffusion coefficient for the proton-lithium counter-diffusion was calculated by the Boltzmann-Matano method and the relationships between the diffusion coefficient, the proton-exchange process, and the crystal phases in proton-exchanged LiNbOs were examined. To confirm the validity of the diffusion coefficient calculated from the SIMS data, the depth profiles of the proton concentrations were numerically computed with the calculated diffusion coefficient and the exponential dependence of the diffusion coefficient on the content of lithium benzoate for dilution was reproduced.