Synthesis of Pure La_10-XSr_xSi₆O_27-0.5x Apatites Using an Optimized Sol-Gel Process

Abstract

Apatite-type lanthanum silicates draw researcher’s attention due to their good performances as electrolyte materials for IT-SOFC (intermediate temperature solid oxide fuel cells). In this paper we present the synthesis and characterization of Sr-doped La10Si6O27 (LSO) prepared through an optimized water-based sol-gel process. The parameters involved in this process have been investigated to obtain high purity, high crystallinity powders. The mechanisms of the sol-gel reactions that underlie the quality of the sol are discussed. The developed sol gel process allows to obtain pure apatite structures through a calcination step of 2 hours at a temperature as low as 800℃. The resulting materials were characterized by scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy. Ionic conductivities have been measured after sintering at 1500℃ and the effect of the Sr-doping has been investigated. The results show that the ionic conductivity is thermally activated and values lies between 4.5×10-2 and 1×10-6 Scm-1 at 873 K as a function of the composition and powder preparation conditions.

Estudo de síntese de silicato de lantânio tipo apatita pelo método sol-gel seguido de precipitação de Na₂SiO₃

“…Desde então, muitos pesquisadores têm se interessado por este material devido às suas propriedades fundamentalmente diferentes dos condutores iônicos tradicionais, como a zircônia estabilizada. Uma característica peculiar é a presença de íons O 2intersticiais (49,50) . (19) .…”