Vanadium-substituted Sm2Ti2O7 pyrochlore. Insight into the structure and electrical conductivity under oxidizing and highly reducing atmosphere

With the aim to increase the conductivity of Sm2Ti2O7 in reducing atmosphere characteristic to the anodic side of the SOFC by partial substitution of titanium site with vanadium, crystalline phases, reduction behavior and transport properties of vanadium-doped Sm2Ti2O7 were investigated in this study. Sm2Ti2-xVxO7±δ (x = 0; 0.1; 0.2) powders have been synthesized using a modified Pechini method. After thermal treatment in air, the presence of monoclinic secondary phase was evidenced by X-ray diffraction analysis and Raman spectroscopy, while thermal treatment in 2% H2/Ar mixture led to single-phase pyrochlore structures. H2-TPR analysis revealed the high reducibility of vanadium-substituted sample. The electrical conductivities of the investigated sample in air are quite small, mainly due to the presence of secondary phase. The decrease in oxygen partial pressure led to a high increase in overall conductivity due to the n-type electronic component. Sample with 5% V on Ti exhibited the highest increase in conductivity when switching from air to hydrogen-containing atmosphere. •Highly reducible vanadium-substituted Sm2Ti2O7 have been synthesized.•Thermal treatment under hydrogen led to the formation of pure pyrochlore phase.•- Sample with 5% V on Ti exhibited the highest increase in conductivity when switching from air to reducing atmosphere.