Rare-earth tungstates have recently attracted significant attention due to its high-temperature proton or mixed proton-electron conductivity. The proton conductivity in La6WO12 decreased with an increase of doping level, yielding some trapping effect in doped systems. In this proposal, we propose to carry out an in-situ neutron diffraction experiment on (CaxLa1-x) ~6WO12-d; (x = 0, and 0.05) samples under humid (D2O+Ar) atmosphere at different temperatures (ambient -1000°C). This in-situ study will provide us with a deeper understanding of proton transport (both kinetics and dynamics) in the bulk material.