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

The applicability of perovskite-type SrVO_3-δ 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 SrV_1-y Ti_y O_3-δ (y=0-0.9) perovskites is demonstrated to result in a gradual shift of the upper-p(O₂ ) phase stability boundary toward oxidizing conditions: from ≈10^-15  bar at 900 °C for undoped SrVO_3-δ 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 SrV_0.7 Ti_0.3 O_3-δ and SrV_0.5 Ti_0.5 O_3-δ at 900 °C remain as high as 80 and 20 S cm^-1 , respectively, and is essentially independent of p(O₂ ) within the phase-stability domain. Combined XRD, thermogravimetric analysis, and electrical studies revealed very sluggish kinetics of oxidation of SrV_0.5 Ti_0.5 O_3-δ ceramics under inert gas conditions and a nearly reversible behavior after exposure to an inert atmosphere at elevated temperatures. Substitution by titanium in the SrV_1-y Ti_y O_3-δ 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 SrV_1-y Ti_y O_3-δ series are discussed in combination with the simulated defect chemistry of solid solutions.