Dense apatite type lanthanumsilicate LSO (La9.33Si6O26) electrolyte and the Al-, Fe- andMg-doped compositions
LASO (La9.83Al1.5Si4.5O26), LFSO (La9.83Fe1.5Si4.5O26), and LMSO (La9.93Mg0.9Si5.1O26) 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 b LASO ≤ LMSO.
The diffusivities of the apatite type lanthanumsilicate (ATLS) electrolyte materials are higher compared to yttria
stabilized zirconia which is the state-of-the-art electrolyte material. The activation enthalpy for oxygen diffusion
in YSZ is higher as compared to the ATLS used in this study. Conductivity studies were also made on samples of
the same composition and density. We observed that aluminium- and magnesium-doped samples have better
conductivity than the undoped counterpart. The role of iron on the conduction mechanism is unclear, but it
shows a positive influence on the conductivity. This behaviour is in agreement with conductivity measurement
results in the literature, where