Hydrogen Permeability in Sintered CeO2 at High Temperatures

It was found that the sintered , which was not perovskite‐type but fluorite‐type, permeated hydrogen under atmosphere at 1050–1800 K. Three tube‐shaped specimens (ϕ 0.287 × 0.894 cm) (SP I, SP II, SP), the lengths of which were 1.40, 0.37, and 1.45 cm, were prepared. The nonexistence of micropores in specimens was confirmed by supplement of to the outside of SP at 1650–1820 K. was supplied to the outsides of SP I and SP II and Ar gas wasallowed to flow to the inside of them. The flow rate to SP I was , and the flow to SP II was controlled so that the hydrogen concentrations measured by a gas chromatograph were of the same value. After the calculation of , , and concentrations in an equilibrium state inside and outside SP I and SP II and the elimination of mechanically leaked and permeated hydrogen through the supporting materials (Pt rings, alumina tube, and disk), the atomic hydrogen permeability, , was determined. The hydrogen partial pressures in the outside and inside were and to 1.53 × 10−3 atm at 1050–1800 K. Log increases with rising temperature, T , while it is not proportional to 1/ T . As the electronic conduction in is considerably higher at low oxygen partial pressure, there is a possibility that is an electron‐proton mixed conductor under atmosphere at high temperatures.