Compromising Between Phase Stability and Electrical Performance: SrVO3-SrTiO3 Solid Solutions as Solid Oxide Fuel Cell Anode Components

The applicability of perovskite-type SrVO3-delta in high-temperature electrochemical energy conversion technology is hampered by the limited stability domain of the perovskite phase. The aim of the present work was to find a compromise between the phase stability and electrical performance by designing solid solutions in the SrVO3-SrTiO3 system. Increasing titanium content in SrV1-yTiyO3-delta (y=0-0.9) perovskites is demonstrated to result in a gradual shift of the upper-p(O-2) phase stability boundary toward oxidizing conditions: from approximate to 10(-15) bar at 900 degrees C for undoped SrVO3-delta to approximate to 10(-11)-10(-5) bar for y=0.3-0.5. Although the improvement in the phase stability is accompanied by a decrease in electrical conductivity, the conductivities of SrV0.7Ti0.3O3-delta and SrV0.5Ti0.5O3-delta at 900 degrees C remain as high as 80 and 20 S cm(-1), respectively, and is essentially independent of p(O-2) within the phase-stability domain. Combined XRD, thermogravimetric analysis, and electrical studies revealed very sluggish kinetics of oxidation of SrV0.5Ti0.5O3-delta ceramics under inert gas conditions and a nearly reversible behavior after exposure to an inert atmosphere at elevated temperatures. Substitution by titanium in the SrV1-yTiyO3-delta system results also in a decrease of oxygen deficiency in perovskite lattice and a favorable suppression of thermochemical expansion. Variations of oxygen nonstoichiometry and electrical properties in the SrV1-yTiyO3-delta series are discussed in combination with the simulated defect chemistry of solid solutions.