Preparation and property-performance relationships in samarium-doped ceria nanopowders for solid oxide fuel cell electrolytes

▶ A compositional series of high purity, nanoparticulate SDC materials was successfully prepared by a low temperature, inexpensive citrate complexation method in order to perform a detailed study of the effect of chemical composition, sintering temperature and sintering time on the densification, grain structure and ionic conductivity of the resulting dense pellets. ▶ Crystallization of the SDC product occurred from the gel at a temperature below 300 °C to give foam-like, single-phase materials with high porosity and with primary crystalline particles of about 10 nm diameter. ▶ Densities of over 95% of theoretical were achieved for all three compositions after sintering at 1400 °C or higher for 4 h or longer and both density and average grain size increased with increasing sintering temperature and sintering time. Samples sintered at 1400 °C for 6 h or 1450 °C for 4 h showed excellent microstructure for all compositions. ▶ Arrhenius-type plots of electrolyte conductivity showed an inflexion at around 500 °C and this was interpreted in terms of a defect association enthalpy, ΔHa, and an oxygen migration enthalpy, ΔHm. ΔHa was less sensitive to Sm content and had values of around 0.4 eV. ΔHm increased significantly with %Sm and had values of 0.4-0.7 eV. ▶ At 600 °C, the highest total conductivity was 1.81 × 10−2 S cm−1 for the 20SDC sample sintered at 1450 °C for 6 h.