Oxygen self-diffusion and conductivity measurements in apatite type electrolyte materials for SOFCs

Abstract

Abstract Dense apatite type lanthanum silicate LSO (La 9.33 Si 6 O 26 ) electrolyte and the Al-, Fe- and Mg-doped compositions LASO (La 9.83 Al 1.5 Si 4.5 O 26 ), LFSO (La 9.83 Fe 1.5 Si 4.5 O 26 ), and LMSO (La 9.93 Mg 0.9 Si 5.1 O 26 ) have been prepared and investigated in this work in terms of their oxygen self-diffusion and total conductivity. Oxygen self-diffusivities and surface exchange coefficients and the respective activation enthalpies have been estimated and discussed. All samples exhibit a typical Arrhenius behaviour of the surface exchange coefficients meaning that the surface incorporation reaction is thermally activated. The doped samples exhibit higher surface concentrations as well as higher surface exchange coefficients as compared to the undoped sample. This indicates that doping has a direct influence to the oxygen incorporation reaction. It has been found that doping enhances the self-diffusion in all cases as compared to the undoped material. The trend found in this study is LSO «LFSO