Synthesis of apatite type La 10¡x Sr x Si 6 O 27¡0.5x powders for IT-SOFC using solegel process Y. Ma a,b,c,* , N. Fenineche a,c , O. Elkedim b,c , M. Moliere a , H. Liao a , P. Briois a,c a IRTES-LERMPS, UTBM, Site de Sevenans, 90010 Belfort Cedex, France b Femto-ST-MN2S, UTBM, Site de Sevenans, 90010 Belfort Cedex, France c FCLab, UTBM, Site de Belfort, 90010 Belfort Cedex, France article info Article history: Received 31 October 2015 Received in revised form 27 January 2016 Accepted 4 February 2016 Keywords: Solegel processes SOFC Apatite type lanthanum silicates Sr doping abstract Apatite-type lanthanum silicates draw researchers' attention due to their good perfor- mance as electrolyte materials for IT-SOFC (intermediate temperature solid oxide fuel cells). In this paper we present the synthesis of Sr-doped La 10 Si 6 O 27 obtained by optimizing a water-based solegel process. The relevant synthesis parameters have been investigated to get pure, highly crystalline powders. The mechanisms occurring in the solegel reactions are discussed to improve the process of the sol formation. Using this optimized solegel process, pure apatite powders have been obtained by calcination from a temperature as low as 800  C for 2 h and characterized using scanning electron microscopy and X-ray diffraction. The sintering treatment was performed at the temperature of 1500  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  10 2 and 1  10 6 S cm 1 at 873 K as function of the composition and powder preparation conditions. © 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction There is currently a renewal of interest for oxide ionic con- ductors as electrolyte materials in solid oxide fuel cells (SOFCs), which are highly efficient energy conversion systems [1]. These devices generate electrical power directly from the fuel oxidation, the electrolytes being responsible for the transport of the ions produced during the reactions [2e4]. Thus, the characteristics of the solid electrolyte strongly influences the cells performance: it must be dense enough to isolate the gas flux and must have a negligible electronic conductivity. Apatite-type lanthanum silicates having the general formula La 10x Si 6 O 271.5x (LSO) have been investigated as ionic conductors with different stoichiometries i.e. with either oxygen ion deficiency or excess entailed by different doping elements [5e7]. Their typical oxide ion conductivity at intermediate temperature (4 mS cm 1 at 500  C) is higher than that of a typical yttria-stabilized zirconia (YSZ) SOFC electro- lyte (1 mS cm 1 ) [8e11]. * Corresponding author. IRTES-LERMPS, UTBM, Site de Sevenans, 90010 Belfort Cedex, France. Tel.: þ33 753937130, þ33 384583129; fax: þ33 384583286. E-mail address: yangzhou.ma@utbm.fr (Y. Ma). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 41 (2016) 9993 e10000 http://dx.doi.org/10.1016/j.ijhydene.2016.02.006 0360-3199/© 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.