An Investigation of the Crystal Structure and Ionic Pathways of the Hexagonal Perovskite Derivative Ba3-xVMoO8.5

Dylan Tawse, Asma Gilane, Sacha Fop, Alfonso Martinez-Felipe, Falak Sher, Ronald I. Smith, Abbie McLaughlin* (Corresponding Author)

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The hexagonal perovskite derivatives Ba3NbMoO8.5, Ba3NbWO8.5 and Ba3VWO8.5 have recently been reported to exhibit significant oxide ion conductivity. Here we report the synthesis and crystal structure of the hexagonal perovskite derivative Ba3-xVMoO8.5-x. Rietveld refinement from neutron and
X-ray diffraction data show that the cation vacancies are ordered on the M2 site leading to a structure consisting of palmierite-like layers of M1Ox polyhedra separated by vacant octahedral layers. In contrast to other members of the Ba3M’M’’O8.5 family, Ba3-xVMoO8.5-x is not stoichiometric and both
barium and oxygen vacancies are present. Although synthesised in air at elevated temperatures, Ba3-xVMoO8.5-x is unstable at lower temperatures, as illustrated by the formation of BaCO3 and BaMoO4 by heat treatment in air at 400 °C. This precludes measurement of the electrical properties. However,
bond-valence site energy (BVSE) calculations strongly suggest that oxide ion conductivity is present in Ba3-xVMoO8.5-x.
Original languageEnglish
JournalInorganic Chemistry
Publication statusAccepted/In press - 3 Aug 2021

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