Interstitial Oxygen and a Two-Dimensional Migration Pathway in Mo-Substituted Palmierite Ba ₃ V 2−x Mo x O 8+x/2
5 affiliations
- 1Department of Radiation Science and Technology
- 2Delft University of Technology
- 3Inorganic Chemistry Laboratory
- 4University of Oxford
- 5Helmholtz Zentrum Berlin für Materialien und Energie
Abstract
Palmierite oxides are promising oxide-ion conductors, with conductivities exceeding those of related hexagonal perovskite derivatives. However, aliovalent Mo6+ substitution in Ba 3 V 2 O 8 has previously been demonstrated only at high substitution levels. Here, the Ba 3 V 2-x Mo x O 8+x/2 series (0 ≤ x ≤ 0.3) was investigated using X-ray and neutron powder diffraction, 51 V and 17 O solid-state NMR spectroscopy combined with density functional theory (DFT), and bond-valence site-energy (BVSE) calculations. Combined Rietveld refinement reveals that Mo6+ substitution introduces a charge-compensating interstitial oxygen site (O3) at x = 0.3, transforming isolated (V, Mo)O 4 tetrahedra into corner-sharing polyhedra with mixed coordination. DFT-supported 17 O NMR identifies additional oxygen environments associated with Mo in four- and five-fold coordination, suggesting oxygen bridges between adjacent MoO5 polyhedra. 51 V NMR confirms predominantly tetrahedral vanadium coordination, alongside a minority V environment , distorted by occupation of a nearby O3 site. BVSE calculations indicate that O3 bridges neighboring polyhedra in the abplane, enabling a low-barrier, two-dimensional oxide-ion migration pathway involving apical O1 and interstitial O3 sites. These findings establish interstitial oxygen incorporation as the key structural mechanism facilitating low-barrier two-dimensional oxide-ion transport at low Mo substitution levels in the palmierite family, with broader implications for hexagonal perovskite ionic conductors.
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BibTeX
@misc{biffo2026interstitial,
title = {{Interstitial Oxygen and a Two-Dimensional Migration Pathway in Mo-Substituted Palmierite Ba ₃ V 2−x Mo x O 8+x/2}},
author = {Abdulkadir Olatunbosun Biffo and Anastasia K. Lavrinenko and Hailin Ma and Shengnan Zhang and Alexandros Vasileiadis and Theodosios Famprikis and Pedro B. Groszewicz},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010854/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010854/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Interstitial Oxygen and a Two-Dimensional Migration Pathway in Mo-Substituted Palmierite Ba ₃ V 2−x Mo x O 8+x/2
AU - Abdulkadir Olatunbosun Biffo
AU - Anastasia K. Lavrinenko
AU - Hailin Ma
AU - Shengnan Zhang
AU - Alexandros Vasileiadis
AU - Theodosios Famprikis
AU - Pedro B. Groszewicz
PY - 2026
DA - 2026/10/22
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010854/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010854/v1
AB - Palmierite oxides are promising oxide-ion conductors, with conductivities exceeding those of related hexagonal perovskite derivatives. However, aliovalent Mo6+ substitution in Ba 3 V 2 O 8 has previously been demonstrated only at high substitution levels. Here, the Ba 3 V 2-x Mo x O 8+x/2 series (0 ≤ x ≤ 0.3) was investigated using X-ray and neutron powder diffraction, 51 V and 17 O solid-state NMR spectroscopy combined with density functional theory (DFT), and bond-valence site-energy (BVSE) calculations. Combined Rietveld refinement reveals that Mo6+ substitution introduces a charge-compensating interstitial oxygen site (O3) at x = 0.3, transforming isolated (V, Mo)O 4 tetrahedra into corner-sharing polyhedra with mixed coordination. DFT-supported 17 O NMR identifies additional oxygen environments associated with Mo in four- and five-fold coordination, suggesting oxygen bridges between adjacent MoO5 polyhedra. 51 V NMR confirms predominantly tetrahedral vanadium coordination, alongside a minority V environment , distorted by occupation of a nearby O3 site. BVSE calculations indicate that O3 bridges neighboring polyhedra in the abplane, enabling a low-barrier, two-dimensional oxide-ion migration pathway involving apical O1 and interstitial O3 sites. These findings establish interstitial oxygen incorporation as the key structural mechanism facilitating low-barrier two-dimensional oxide-ion transport at low Mo substitution levels in the palmierite family, with broader implications for hexagonal perovskite ionic conductors.
ER -