Proton conduction in layered perovskite oxides

Investigation of the electrical conductivity behavior of layered perovskite oxides, $H_2Ln_2Ti_3O_{10}$ (Ln = La, Nd, Sm and Gd), has revealed that the materials exhibit moderate conductivity $(\sim 10^{-5}\hspace{2mm} \Omega^{-1} cm^{-1}$ at 400°C) in hydrogen atmosphere, that is likely to be protonic in origin. It is suggested that the anion-deficient layered perovskite, $Ln_2Ti_3O_9$, formed in situ by dehydra- tion, may interact with water vapor in hydrogen atmosphere in a manner analogous to that of yttria-doped $BaCeO_3$ and $SrCeO_3$ giving rise to the protonic conductivity. $HLa_2Ti_2NbO_{10}$ and $HCa_2Nb_30_{10}$ possessing a slightly different layered perovskite struc- ture, exhibit a higher conductivity $(\sim 10^{-4} - 10^{-3}\Omega^{-1} cm^{-1})$ under the same conditions