Elaboration, by tape casting, and thermal characterization of a solid oxide fuel half-cell for low temperature applications

In the past years, a major interest has been devoted to decrease the working temperature of solid oxide fuel cell (SOFC) down to about 700 °C. In this respect, materials with a high ionic conduction at intermediate temperature have to be found and the processes to elaborate fuel cells, using these new materials, have to be developed.Apatite materials (La_10−xSr_x(SiO₄)₆O_2±δ) are attractive candidates for solid electrolyte working at intermediate temperature. The ceramic powder was produced by solid state reaction and was tape cast to obtain green sheets.Concerning the cathode, a perovskite oxide (La_1−xSr_xMn_1−yCo_yO_3−δ) has been chosen. The perovskite powder was also shaped by tape casting with the introduction of a pore forming agent (corn-starch) to obtain the required porosity in the sintered cathode.The co-firing of the electrolyte/cathode half-cell in air at 1400 °C-2 h gives a flat sample with a dense apatite (98.2%), a 42.7% porous cathode and neither delamination nor chemical reactivity between electrolyte and cathode materials.The dimensional behaviour of the electrolyte material is stable for an oxygen partial pressure ranging from 10⁻¹⁰ to 0.21 atmosphere, from room temperature to 700 °C. The thermal expansion coefficients of the electrolyte and cathode materials are rather close (Δα = 2.8 × 10⁻⁶ K⁻¹) under air.