OXYGEN PERMEATION, ELECTRICAL-CONDUCTIVITY AND STABILITY OF THE PEROVSKITE OXIDE LA0.2SR0.8CU0.4CO0.6O3-X

The cubic perovskite La0.2Sr0.8Cu0.4Co0.6O3-x has high electronic and ionic conductivity at high temperatures. The electronic conductivity i nitially increases with increasing temperature but then decreases due to loss of oxygen atoms from the structure. The oxygen permeability me asured on disc membranes is comparable to values reported for other co balt-containing perovskite oxides with high strontium content. The per meation flux decreases with time due to a transformation of the disord ered cubic perovskite to an ordered structure related to Brownmillerit e. This ordered structure is stable below 975 degrees C in an oxygen p artial pressure pO(2) = 0.01 atm. Membranes that have been maintained at high temperature in an oxygen partial pressure gradient for >400 h show decomposition to a multi-phase assemblage that includes non-perov skite strontium cuprates. This decomposition may also contribute to th e flux decline.