Solid State Ionics, Vol.143, No.1, 117-123, 2001
Proton conduction in non-perovskite-type oxides at elevated temperatures
Ionic conduction in two non-perovskite-oxides, fluorite-related-type lanthanum tungsten oxide and aragonite-structure lanthanum berate, was investigated at elevated temperatures. LaxWO3+1.5x (x congruent to 6) with a fluorite-related structure showed protonic conduction under hydrogen-containing atmospheres. The emf of a hydrogen concentration cell showed that the ionic transport number in hydrogen was about 0.7-0.9. The result of an electrochemical hydrogen pumping experiment using LaxWO3+1.5x directly evidenced the protonic conduction in this oxide. Partial substitution of Zr for La lowered the electrical conductivity, while the influence of Nd substitution was small. The electrical conductivity of the aragonite-type oxide salt LaBO3 increased by doping with Sr, although the conductivities of these ceramics were not high. The emf values of a hydrogen concentration cell using lanthanum berate (LaBO3) were stable and close to theoretical values, suggesting that electrical conduction in this oxide was due to protons.
Keywords:proton conduction;lanthanum tungsten oxide;lanthanum borate;concentration cell;electrochemical hydrogen pumping