Direct synthesis of La_9.33Si₆O₂₆ ultrafine powder via sol–gel self-combustion method

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• 作者：Changan Tian ; Junliang Liu ; Jun Cai ; Yanwei Zeng
• 关键词：La_9.33Si₆O₂₆ ; Ultrafine powder ; Synthesis ; Self-combustion
• 刊名：Journal of Alloys and Compounds
• 出版年：2008
• 出版时间：30 June 2008
• 年：2008
• 卷：458
• 期：1-2
• 页码：378-382
• 全文大小：435 K

文摘

Single phase La_9.33Si₆O₂₆ ultrafine powder, as a kind of highly activated precursor to prepare medium-to-low temperature electrolyte for solid oxide fuel cells (SOFCs), has been successfully synthesized via a non-aqueous sol–gel and self-combustion approach from the starting materials: lanthanum nitrate (La(NO₃)₃·6H₂O), citric acid, ethylene glycol (EG), tetraethyl orthosilicate (TEOS) and ammonium nitrate. The details of gel's self-combustion were investigated by DTA–TG and the structural characterization of as-synthesized powder from self-combustion was performed by XRD and SEM. The results show that La_9.33Si₆O₂₆ single phase of apatite-type crystal structure can be directly synthesized by sol–gel self-combustion method without further calcinations on the condition that the molar ratio (R) of NO₃⁻ to citric acid and ethylene glycol being 6:1. Such powders composed of well-dispersed particles with an average size of 200 nm and a specific surface area of 5.54 m²/g. It can be sintered to 90 % of its theoretical density at 1500 °C for 10 h, about 200 °C lower than the sintering temperature for the powder derived from traditional solid reactions. The sintered material has a thermal expansion coefficient of 9.2 × 10⁻⁶ K⁻¹ between room temperature and 800 °C.