Enhanced sinterability of mechanical alloyed La9.33Si2Ge4O26 oxyapatite powders for IT-SOFC electrolytes

Dense oxyapatite-based La9.33Si2Ge4O26 electrolytes have been successfully prepared by electrical sintering at 1400 °C in static air for 1 h from dry milling La2O3, SiO2 and GeO2 powders, in adequate atomic proportions, at 350 rpm for 15 h, under controlled environmental conditions, in a planetary ball mill. The densification behaviour of apatite-type phase La9.33Si2Ge4O26 powders synthesized by mechanical alloying was investigated through microstructural evolution with sintering temperature by means of XRD and SEM/EDS analyses. The content of germanium in the sintered samples remained almost constant, suggesting that its incorporation in the apatite phase hinders the high temperature (>1250 °C) volatilization process.