Defect chemistry and oxygen permeation property of Pr₂Ni_0.75Cu_0.25O₄ oxide doped with Ga

Mixed conductivity and oxygen permeation property in Pr₂Ni_0.75Cu_0.25Ga_0.05O₄ were investigated. After examining various Ga concentrations, it was found that cation excess composition of Pr₂Ni_0.75Cu_0.25Ga_0.05O₄ achieved the highest oxygen permeability of 298 μmol·min^{- 1}·cm^{- 2} (6.68cc·min^{- 1}·cm^{- 2}) at 1273 K from air to He with a 0.5 mm thickness. The oxygen permeability of Pr₂Ni_0.75Cu_0.25Ga_0.05O₄ increased with increasing the activity of surface catalyst and the highest permeation was achieved when La_0.9Sr_0.1Co_0.8Fe_0.2O₃ was used for the surface catalyst. The oxygen nonstoichiometry was further studied by using thermogravimetry. It was confirmed that the excess amount of oxygen was introduced at high P_O2 range, which might be the origin of the high oxygen permeation rate in this oxide.