Redox Stable Conductivity of B-Site Doped SrTiO3 for SOFC Anodes

The stability of solid oxide fuel cell (SOFC) anodes during cycles of reducing and oxidizing environments (redox cycling) is a critical parameter of durability, particularly for portable applications. The standard Ni-YSZ anode is not stable during redox cycles because the volume of Ni substantially increases upon oxidation. This expansion ultimately results in mechanical failure of the fuel cell. To address this limitation, SrTa_xTi_1-xO₃ (STT) has been investigated as a potential material for redox-stable anodes. While Ni is both an e^- conductor and an oxidation catalyst, STT can only provide e^- conduction and a separate catalyst must be added. Dense STT and porous STT-YSZ composites, for x = 0.01, 0.05, and 0.10, were sintered in both air at 1873 K and hydrogen at 1773 K. X-ray diffraction (XRD) indicated a single perovskite phase for STT and that STT and YSZ are chemically compatible. Conductivities greater than 1 S·cm^-1 were achieved for porous STT-YSZ with x = 0.01 and 0.05 when initially reduced at 1773 K. Without this high temperature reduction, conductivity was too low for SOFC anode applications. STT with x = 0.01 demonstrated the highest redox stable conductivity with a porous conductivity of 0.9 S·cm^-1 after oxidation at 1273 K.