Hydrogen permeability in (CeO2)0.9(GdO1.5)0.1 at high temperatures

The atomic hydrogen (1/2H2) permeability, JH, in (CeO2)0.9(GdO1.5)0.1 (fluorite-type) was measured at 1800–800 K. Two tubular specimens (SP(L), SP(S)) of different lengths sintered at 1970 K in air were used to eliminate the permeation through supporting materials (Pt rings, alumina tube and alumina disk). The JH was 2.81×10−6–1.50×10−8/mol h−1 cm−1, when it was assumed that PH2=7.34×103 Pa and PH2O=2.28×103 Pa outside of both specimens and that the Ar flow rates to the inside of SP(L) and SP(S) were 20.9 and 9.4–16.0 cm3 min−1, respectively. LogJH decreased with decreasing temperature and was proportional to the inverse temperature at 1800–1100 and 1100–800 K, and the activation energies were 1.12±0.01 and 0.18±0.01 eV, respectively. (CeO2)0.9(GdO1.5)0.1 would be an electron–proton mixed conductor under H2–H2O atmosphere at high temperatures. The protonic conductivity was roughly calculated from the JH and from the hydrogen partial pressures inside and outside the specimens, its values being 1.4×10−4–7.2×10−7/S cm−1 and 1.2×10−6/S cm−1 at 1070 K.