Preparation and characterization of La9.33Si6O26 powders by molten salt method for solid electrolyte application

Lanthanum silicate La9.33Si6O26 (LSO) powders with more uniform particle and less agglomeration were obtained at a much lower synthesis temperature by the molten salt method than by the solid-state method. LSO ceramic electrolytes were prepared with these powders and characterized as well. The optimal molten salt synthesis conditions are mass ratio of reactants to NaCl of 1:3 and synthesis temperature of 900 degrees C. XRD results showed that when the mass ratio of reactants to NaCl was no more than 1:3, pure LSO phase powder was obtained at 900 degrees C. XRD and XRF results showed that when synthesis temperature was higher than 900 degrees C, a solid solution type LSO powder with Na replacement for La formed at a fixed mass ratio of reactants to NaCl of 1:3. The involvement of Na in LSO lattice might lead to the lattice contraction in powders and deteriorate the conductance of ceramic electrolytes. The ceramic electrolytes prepared from the pure LSO powder via molten salt process exhibited better electrical properties than those from the powder via solid-state method. (C) 2010 Elsevier B.V. All rights reserved.