  In-situ electrochemical impedance spectroscopy was used to study the effect
of lattice volume and strain on the proton conductivity of the yttrium-doped
barium cerate proton conductor by applying the hydrostatic pressure up to 1.25
GPa. An increase from 0.62 eV to 0.73 eV in the activation energy of the bulk
conductivity was found with increasing pressure during a unit cell volume
change of 0.7%, confirming a previously suggested correlation between lattice
volume and proton diffusivity in the crystal lattice. One strategy worth trying
in the future development of the ceramic proton conductors could be to expand
the lattice and potentially lower the activation energy under tensile strain.
