Perovskite-type SrVO₃- and SrTiO₃-based phases exhibit good resistivity to sulfur poisoning and do not catalyze carbon deposition, and are considered therefore as possible alternative anode materials for hydrocarbon-fueled solid oxide fuel cells. SrVO₃ exhibit high electronic conductivity but also a narrow phase stability domain restricted to reducing conditions. On the other hand, SrTiO₃ demonstrates remarkable phase and dimensional stability in a wide range of T-p(O₂) conditions but rather insufficient electrical conductivity. The present work aimed at the development of SrVO₃-SrTiO₃ composite anode materials with emphasis on a compromise between dimensional/microstructural stability and electrical properties.

Initial assessment demonstrated that SrVO₃ and SrTiO₃ form an entire range of solid solutions under reducing conditions. In all cases, exposure to air above 600-700°C resulted in either collapse of perovskite structure (V-rich compositions) or separation of vanadium-containing secondary phases (Ti-rich composition). These phase transformations were accompanied by dimensional changes and were not reversible at temperatures below 1000°C (probably, due to kinetic reasons).

Instability in oxidizing atmospheres complicates the fabrication of anodes in realistic conditions. Therefore, the second approach was to start from oxidized phases and to proceed via in-situ reduction employed for Ni-YSZ cermet anodes. V⁵⁺ substituted in titanium sublattice of SrTiO₃ acts as donor-type dopant and was found to has a limited solid solubility under reducing conditions (~30-35 at.%). In-situ reduction of oxidized SrTi_1-yV_yO_±δ at 900°C is accompanied however by the reduction of vanadium cations, and the resultant conductivity remains too low (< 0.2 S/cm) being comparable to other acceptor-doped strontium titanates.

The next approach was preparation of composite SrVO₃-SrTiO₃ anode materials starting from oxidized phases. The precursors with nominal composition SrTi_1-yV_yO_±δ (y = 0.1-0.4) were thermally treated in air at temperatures not exceeding 1100°C to yield equilibrated phase mixtures comprising SrTiO₃-based perovskite as a main phase and strontium orthovanadate Sr₃(VO₄)₂ as a second major phase. Transformation of strontium orthovanadate on reduction at 900°C into highly-conductive perovskite-type SrVO₃ phase finely distributed in the stable SrTiO₃-based matrix resulted in substantial nearly instant increase of electrical conductivity by orders of magnitude reaching 10-30 S/cm for y = 0.3-0.4. Electrochemical activity of composite anodes applied onto yttria-stabilized zirconia solid electrolyte and infiltrated with a fraction of Ce_0.9Gd_0.1O_2-δ electrolyte component was evaluated by electrochemical impedance spectroscopy using symmetrical cell configuration.