Speaker
Description
Complex perovskite derived oxides are an important emerging class of ionic conducting materials with potential applications in energy technologies including fuel cells, batteries, and separation membranes. The high temperature phase γ-Ba4Nb2O9 is one such complex oxide which shows proton and oxide ionic conduction.
Recently we have shown that two new compositional series with the previously unique γ-Ba4Nb2O9 type structure, γ-Ba4VxTa2-xO9 and γ-Ba4VxNb2-xO9 (x = 0-2/3),can form [1]. Undoped Ba4Ta2O9 forms a 6H-perovskite type phase, but with sufficient V doping the γ-type phase is thermodynamically preferred and possibly more stable than γ-Ba4Nb2O9, forming at a 200 °C lower synthesis temperature. This is explained by the fact that Nb5+ ions in γ-Ba4Nb2O9 simultaneously occupy 4-, 5- and 6-coordinate sites in the oxide sublattice, which is less stable than allowing smaller V5+ to occupy the former and larger Ta5+ to occupy the latter. We characterised the structures of the new phases using a combination of X-ray and neutron powder diffraction. All compositions hydrate rapidly and extensively (up to 1/3 H2O per formula unit) under ambient conditions, like the parent γ-Ba4Nb2O9 phase, and show moderate but improved mixed-ionic electronic conduction. At lower temperatures the ionic conduction is significantly protonic, where hydration is maintained. We also show that these new vanadium containing phases have higher total conductivities than the parent γ-Ba4Nb2O9 compound.
[1] AJ Brown, B Schwaighofer, M Avdeev, B Johannessen, IR Evans and CD Ling, Chemistry of Materials, available online (2021). DOI: 10.1021/acs.chemmater.1c02340
| Condition of submission | Yes |
|---|---|
| Level of Expertise | Student |
| Which facility did you use for your research | Australian Centre for Neutron Scattering |
| Students Only - Are you interested in AINSE student funding | Yes |
| Presenter Gender | Man |
| Pronouns | He/Him |
| Do you wish to take part in the Student Poster Slam | No |
