The comparison of SrTi0.98Nb0.02O3-δ-CeO2 and SrTi0.98Nb0.02O3-δ-YSZ composites for use in SOFC anodes

Composites of Nb-doped strontium titanate mixed with yttria-stabilized zirconia or cerium oxide in 50:50, 70:30 and 85:15 weight ratios were evaluated as possible anode/electrolyte interface materials for solid oxide fuel cells in terms of chemical compatibility, electrical conductivity and mechanical properties. It has been shown that composite samples prepared by typical powder-mixing methods remain single-phase up to 1400A degrees C. The electrical conductivity of these composites, regardless of their composition and fabrication conditions, is lower than the conductivity of pure SrTi0.98Nb0.02O3-delta, but in most cases sufficient for solid oxide fuel cells anode application. The best properties are found for samples reduced at 1400A degrees C for 10 h in H-2 atmosphere. The observations made by scanning electron microscope suggest that the grains of both phases are well-distributed throughout the whole volume of the investigated samples, and that the composites with CeO2 better adhere to the electrolyte surface. The electrical results confirm that composites with at most 30 wt % of YSZ/CeO2 phase fulfill the anode requirements. However, the fuel cell performance tests indicate that the application of composite with CeO2 results in the lower power density than the application of the composite with YSZ.