Development of Proton Conducting SOFCs Based on LaNbO4 Electrolyte - Status in Norway

High temperature proton conducting solid oxide fuel cells (PC-SOFCs) are in a developing state. Electrolytes in these cells should exhibit proton conductivity with essentially no electronic and little other ionic conductivity, as well as long-term stability in acidic atmospheres. Acceptor substituted rare-earth ortho-niobates and ortho-tantalates were recently demonstrated to exhibit proton conductivity in wet atmospheres, with a maximum of similar to 10(-3) S cm(-1) for 1% Ca-doped LaNbO4. This modest proton conductivity requires that the electrolyte thickness is in the micron range to reach acceptable PC-SOFC performances. The long-term chemical stability and a proton transference number close to unity make these materials highly interesting for high temperature fuel cell applications, in contrast to the more investigated acceptor-doped BaCeO3 that shows instability towards acidic atmospheres. Here, we describe collaborative efforts between Norwegian partners: SINTEF, Norwegian University of Science and Technology (NTNU) and the University of Oslo for developments towards a fuel cell based on LaNbO4. This comprises identification of materials for the electrodes, interconnect and sealing, optimisation of the microstructures of all cell components, development of shaping processes and design of the fuel cell stack. We address the crucial technological issues of building and testing a PC-SOFC stack, as well as the comprehensive fundamental understanding of all the processes involved - from fabrication and behaviour of individual components to fabrication of PC-SOFC fuel cell stacks.