Speaker
Description
Apatite-type rare-earth silicates are one of the most promising materials as electrolyte for oxide fuel cells (SOFCs) applications, due to their high ionic conductivity along the c-axis apatite structure. Previous studies have shown that this ionic conductivity is about one order of magnitude greater for c-axis-oriented oxyapatite. The aim of this work is to determine the optimal operating conditions for the production of oriented La9.33+x(SiO4)6O2+3x/2 by reactive diffusion between La2SiO5 and SiO2 layers.
In a first step, the synthesis of La2SiO5 was studied from solid-state reaction between high purity powders of La2O3 and SiO2. High temperatures (1700°C) and prolonged synthesis time are reported in the literature. In others systems it has been shown that the solid-state reaction pathways and the phase purity could differ according to the particle size and the size ratio of reactive powders. Therefore, the influence of these two parameters was more particularly studied, using in situ high-temperature X–ray analysis and Rietveld refinement. By using an alternative synthesis method with a colloidal silica precursor, the purity levels achieved at 1500°C after 10 hours were very satisfactory, with La2SiO5 content more than 90%. A reaction mechanism was proposed and supported by chemical kinetics analysis, highlighting the strong impact of the size ratio (La2O3/SiO2: 1µm/0.002µm) to improve the reactivity and La2SiO5 phase formation.
In a second step reactive diffusion between La2SiO5 and SiO2 layers was studied, and gave promising preliminary results through the successful formation of c axis-oriented oxyapatite
| Speaker Country | France |
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