Water uptake of nanocrystalline ceria: weight and conductance effects

The nature of water adsorption on the surface of nanocrystalline ceria powder (particle size of ∼12 nm) was investigated by means of thermogravimetric techniques as a function of temperature, water partial pressure, doping content and synthesis route. A significant amount of water was found to be adsorbed on the surface of nanocrystalline powder even under nominally dry atmosphere in a broad range of temperatures (300–600 °C), irrespective of doping. The nanocrystalline ceria sinter bodies (grain size of ∼30 nm with ∼90% density) also exhibited water adsorption which can be attributed to open pores rather than to grain boundaries. The impedance measurements clearly indicated, however, that the contribution of the adsorbed water to the measured conductivity of nanocrystalline ceria ceramics is negligible under the condition of the measurements even at high water vapour partial pressures.