Synthesis of apatite type La10-xSrxSi6O27-0.5x powders for IT-SOFC using sol-gel process

Apatite-type lanthanum silicates draw researchers' attention due to their good performance as electrolyte materials for IT-SOFC (intermediate temperature solid oxide fuel cells). In this paper we present the synthesis of Sr-doped La10Si6O27 obtained by optimizing a water-based sol-gel process. The relevant synthesis parameters have been investigated to get pure, highly crystalline powders. The mechanisms occurring in the sol-gel reactions are discussed to improve the process of the sol formation. Using this optimized sol-gel process, pure apatite powders have been obtained by calcination from a temperature as low as 800 degrees C for 2 h and characterized using scanning electron microscopy and X-ray diffraction. The sintering treatment was performed at the temperature of 1500 degrees C leading to well-crystallized electrolytes likely to be used in fuel cell applications. Ionic conductivities have been measured in order to investigate the effect of the Sr-doping. The results show that the ionic conductivity is thermally activated and its value lies between 3 x 10(-2) and 1 x 10(-6) S cm(-1) at 873 K as function of the composition and powder preparation conditions. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.