Investigation of Enhanced Ionic Conductivity in La-doped Sr3V2O8

Solid oxide ion and proton conductors are important materials with applications in a range of hydrogen-based energy technologies. To make these technologies more economical and durable, it is important to develop new ionic conductors with high conductivities at reduced temperatures (≤ 600 °C). We have recently reported high oxide ion and proton conductivity in palmierite Sr3V2O8. The present study explores the potential of further enhancing its ionic conductivity via targeted chemical doping, specifically by substituting Sr2+ for La3+ to form the solid solution Sr(3-3x)La(2x)V2O8. Preliminary electrical characterization has revealed a two orders of magnitude increase in oxide ion conductivity with La3+ doping. However, an intriguing finding is that proton conductivity is completely suppressed. This suggests the formation of both cation vacancies and interstitial oxygen defects in the doped material. We propose to perform neutron diffraction measurements as function of temperature to verify the presence of oxygen interstitials and understand the doping mechanism brought about by La3+ → Sr2+ substitution and its impact on the significant increase in oxide ion conductivity. This study will be important in providing design rules for the enhancement of the ionic conduction in this new class of conductors.