Novel chemical reaction co-precipitation method for the synthesis of apatite-type lanthanum silicate as an electrolyte in SOFC

Abstract

Apatite-type lanthanum silicates have promising performance as electrolyte materials for IT-SOFC. A novel co-precipitation method, based on chemical reaction, is employed in the synthesis process. The reaction products: La(OH)3 and SiO2 are used as precursors of apatite synthesis process. The precursors are mixed in molecular scale which provide much conducive to formation reaction. The pure apatite phase composition is obtained with quite moderate temperature of 700 °C for 6 h which shows considerable ionic conductivity performance. The conductivity decreases when you increase the calcination temperature in according with XRD measurement. The XRD measurement shows the presence of impurity phase when the calcination temperature increases. Furthermore, the activation energies of the apatite synthesized in this study are rather high in comparison with the literature data, which can be attributed to a presence of the impurity phase. The ionic conductivity is controlled by the grain boundaries contributions for low calcination temperature and by the grains contributions for the sample calcined at 1000 °C.