Unlocking the Potential of Palmierite Oxides: High Oxide Ion Conductivity via Induced Interstitial Defects
Dylan N. Tawse, Sacha Fop, John Still, Oscar J. B. Ballantyne, C. Ritter, Ying Zhou, James A. Dawson, Abbie C. Mclaughlin
Abstract
High Resolution Image Download MS PowerPoint Slide Hexagonal perovskite derivatives such as Ba 7 Nb 4 MoO 20 and Ba 3 NbMoO 8.5 have recently been reported to exhibit high oxide ion conductivity and have potential applications in next-generation solid oxide fuel cells. In contrast, Ba 3 V 2 O 8 and Sr 3 V 2 O 8 that crystallize with the structurally related palmierite structure show oxide ion conductivities orders of magnitude lower. Here we use design principles to enhance the oxide ion conductivity in palmierites. By replacing V 5+ with two cations that are known to display flexible coordination (Mo 6+ and Ti 4+ ) and manipulating the ratio of Mo 6+:Ti 4+ to insert interstitial oxygen, a high oxide ion conductivity of 3.96 × 10 –3 S cm –1 at 600 °C is observed in Ba 3 Ti 0.9 Mo 1.1 O 8.1, two orders of magnitude higher than previously reported in palmierites. The oxide ion conductivity of Ba 3 Ti 0.9 Mo 1.1 O 8.1 is also higher than that previously reported for both Ba 7 Nb 4 MoO 20 and Ba 3 NbMoO 8.5 at 600 °C. Introducing interstitial oxygen into the [BaO 2+ x ] layer results in a change in the oxide ion transport from a cog-wheel type motion to an interstitialcy mechanism, demonstrating that palmierites are flexible to doping strategies via the introduction of either vacancies or oxide ion interstitials.