Oxide ion conductivity in defect perovskite, Pr₂NiO₄ and its application for solid oxide fuel cells

Oxide ion conductivity in defect perovskite, mainly Pr2NiO4 with K2NiF4 structure, was studied in details. Defect perovskite oxide consists of perovskite block connected series to oxygen deficient block and although it is known that oxygen deficient block traps mobile oxide ion in lattice, interstitial oxygen introduced at rock salt block in Pr₂NiO ₄ shows high mobility resulting in the high oxide ion conductivity. Oxide ion conductivity is much increased by doping Cu and Ga for Ni site and Pr deficient. The observed oxide ion conductivity was high like log (•/Scm¹1) = ¹0.25 at 1173 K. Conducting property of Pr_1.91Ni_0.75Cu_0.21Ga_0.05O ₄(PNCG)/Ce_0.8Sm_0.2O₂(SDC) nano laminated film was further studied and the conductivity was much increased by formation of residual strain and the ion blocking method shows the transport number of the laminated film is almost unity and so high conductivity of PNCG/SDC laminated film could be assigned to pure oxide ion. Application of PNCG for anode of SOFC was further studied and it was found that surface activity of Pr₂NiO₄ doped with Cu and Ni shows high and so superior cathodic property was achieved at low temperature by mixing Pr ₂NiO₄ with SDC. The maximum power density of the cell using LaGaO₃ thin film electrolyte was achieved at 0.12W/cm ² at 673 K.