OXYGEN PERMEABILITY IN ZRO2-TIO2-Y2O3 SYSTEM

The oxygen permeability of yttria-stabilized zirconia containing 7.5 and 10 mol%TiO2 was measured under low oxygen partial pressure and at high temperatures up to 1500-degrees-C. The measured oxygen permeability increases with decreasing oxygen partial pressure according to P(O2)-1/6. This proportionality indicates that the n-type electronic conduction in the yttria-stabilized zirconia containing TiO2 is due to the electron hopping between Ti4+ and Ti3+ ions. The activation energy of 1.9 eV is obtained for the electronic conduction. At 1000-degrees-C, the contribution of the electronic conduction is negligibly small even under low oxygen partial pressure. From these results, ZrO2-TiO2-Y2O3 system is not so promising material for electrode in SOFC. As this system is stable and has a high oxygen permeability at high temperatures up to 2000-degrees-C, it is the promising material as a membrane for a direct water splitting at high temperatures to produce hydrogen.