OXYGEN PERMEATION IN ZRO2-CEO2-CAO FOR APPLICATION TO OXYGEN SEPARATION FROM THERMALLY DECOMPOSED H2O

To prepare a high-temperature oxygen permeation membrane, the enhancem ent of oxygen permeation rate in calucia-stabilized zirconia by CeO2 d oping was studied. Two tube-shaped specimens (phi 1.3 x 0.9 cm), 0.5 a nd 1.5 cm in length, were used to measure the bulk oxygen permeability from a N-2 + O-2 gas mixture into He, eliminating the oxygen permeati on caused by the short-circuiting; effect of Pt O-rings which were use d to seal the interface of specimens and alumina tubes. Since the oxyg en source was N-2 + O-2, mechanical oxygen leakage was estimated from nitrogen leakage into He. From the measurement of oxygen permeations a t 1100 similar to 1800 K in [(ZrO2)(1-x)(CeO2)(x)](0.9)(CaO)(0.1) (X = 0.1 similar to 1.0), it was shown that the oxygen permeability, Jr, w hich was normalized by the temperature and the oxygen partial pressure s outside and inside the specimen, and the electronic conductivity whi ch was at 1 atm of oxygen partial pressure and was calculated from Jr, increased exponentially with temperature and X for X = less than or e qual to 0.5 while showing saturation tendency for X > 0.5. The oxygen separation membrane of X = 0.4 similar to 0.5 seems reasonable because of the remarkable permeability and lower content of CeO2 which has hi gher vapor pressure at high temperature.