On the proton conductivity in pure and gadolinium doped nanocrystalline cerium oxide.

Conductivity measurements were performed on microcrystalline and nanocrystalline ceria (undoped and doped) in dry as well as wet atmosphere. Below 200-250 °C, the nanocrystalline samples exhibit an enhanced total conductivity under wet conditions, which increases with decreasing temperature. In addition, thermo-gravimetric analysis revealed a strong water uptake below 200 °C. DC-polarization measurements confirm the ionic character of conductivity in the nanocrystalline samples at low temperatures. The role of both grain boundaries and residual porosity on the enhanced conductivity below 200 °C is discussed.