Proton conductivity of hydrated tin dioxide (SnO2·nH2O) was investigated at 100–150C under water vapor pressure up to 0.5MPa, and was compared with that of hydrated zirconia (ZrO2·nH2O). High proton conductivities above 10-2S/cm were observed in both hydrates at 150C under high water vapor pressures. The conductivity decreased with a decrease in water vapor pressure at 130–150C, but the decrease of conductivity in SnO2·nH2O was smaller than that in ZrO2·nH2O. The SnO2·nH2O showed a good recovering property of conductivity after drying at 150C, which was not observed for ZrO2·nH2O, suggesting the SnO2·nH2O to be suitable as proton-conductive electrolyte for use at intermediate temperatures. Films of SnO2·nH2O/polymer composites were prepared, and a high conductivity was observed in SnO2·nH2O/R-epoxy resin.

Proton-Conducting Properties of Hydrated Tin Dioxide as an Electrolyte for Fuel Cells at Intermediate Temperature. S.Hara, H.Sakamoto, M.Miyayama, T.Kudo: Solid State Ionics, 2002, 154-155, 679-85