The atomic hydrogen permeability in (CeO2)0.85(CaO)0.15 at high temperatures

The atomic hydrogen permeability, JH, in fluorite-type (CeO2)0.85(CaO)0.15 was measured to confirm the influence of CaO concentration in CeO2 at 1050–1800 K. The decrease of JH with reducing temperature and the proportionality of log JH to inverse temperature are suggested. The estimated activation energies are 1.05±0.01, 1.35±0.02 and 0.22±0.04 eV at 1800–1400, 1400–1250 and 1250–1050 K, respectively. The JH of (CeO2)1−X(CaO)X decreases with increasing X and proportional to X5/2 at 1800–1300 K under H2–H2O atmosphere. H2 is decomposed to 2H+ and 2e− on the surface of the specimen and they permeate it. They hop between oxygen ions and cerium ions, respectively. It would be difficult for H+ to cross over Vö, which was produced by CaO, then JH decreased with increasing X. (CeO2)1−X(CaO)X would be the electron–proton mixed conductor under H2–H2O atmosphere at high temperatures.