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 degrees 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-x)Sr(x)(SiO(4))(6)O(2+/-delta)) 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-x)Sr(x)Mn(1-y)Co(y)O(3-delta)) 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 degrees 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 degrees C. The thermal expansion coefficients of the electrolyte and cathode materials are rather close (Delta alpha = 2.8 x 10(-6)K(-1)) under air. (C) 2009 Elsevier Ltd. All rights reserved.