Novel high temperature proton conducting fuel cells: Production of La0.995Sr0.005NbO4−δ electrolyte thin films and compatible cathode architectures

For breakthrough development in solid oxide fuel cells, novel cell architectures integrating better performing materials and cost-effective manufacturing processes with potential for mass production must be realised. The present work addresses this on the basis of the recent discovery of acceptor doped rare-earth ortho-niobate proton conductors and the development of a versatile fabrication process. La0.995Sr0.005NbO4−δ/NiO anodes are produced by tape-casting and co-lamination of green layers. Their porosity is finely tuned by using a pyrolyzable pore former. La0.995Sr0.005NbO4−δ electrolytes are spin-coated using ceramic-based suspensions. Fully dense electrolytes with thickness ranging from 9 μm to 26 μm are obtained after sintering in air at 1350 °C. The cathode layers are then screen-printed. To match thermal expansion and to avoid chemical reaction between the functional layers, special attention is paid to the design of cathode architectures. CaTi0.9Fe0.1O3−δ, La2NiO4+δ and La4Ni3O10 mixed oxygen ion and electron conducting oxides are investigated as either monophase or La0.995Sr0.005NbO4−δ-based composite electrodes. The latter gives the whole cell an innovative “semi-monolithic” concept, which can take advantage of the chemical and mechanical stability of La0.995Sr0.005NbO4−δ, as well as of inherent material integration. Most promising cell architectures are finally selected based on thermo-mechanical and chemical compatibility of all functional layers.