New chemical route based on sol–gel process for the synthesis of oxyapatite La9.33Si6O26

The aim of this paper is to advance in the field of the development of low-cost synthesis techniques easy to transfer at an industrial scale for electrolyte functional materials in intermediate temperature solid oxide fuel cells (IT-SOFC). We developed an original sol–gel route to synthesize La9.33Si6O26 oxides. This approach is straightforward, inexpensive, versatile and it produces pure powders with controlled size and morphology. Via sol–gel route, crystallization temperature of such phases are drastically reduced: 800 °C in comparison with 1500 °C in solid-state conventional routes. The dependance of the nature of the phases was studied by varying several parameters as the hydrolysis rate, the volumetric ratio of catalyst to TEOS and the silicon concentration. All these parameters affect the homogeneity of the gel and thus, the purity of the oxides obtained after heat treatment in air. These oxyapatite materials have particle size of about 100 nm after heat treatment at 1000 °C. The use of these powders for ceramic processing allows a decrease of the sintering temperature of more than 200 °C.