Vanadium Electronic Configuration Determination From L2,3 Transition in V-oxide Compounds and Roscoelite

Pierre-Marie Zanetta; Maxwell S Drexler; Isabel F Barton; Thomas J Zega

doi:10.1093/micmic/ozac057

Vanadium Electronic Configuration Determination From L2,3 Transition in V-oxide Compounds and Roscoelite

Microsc Microanal. 2023 Apr 5;29(2):459-469. doi: 10.1093/micmic/ozac057.

Authors

Pierre-Marie Zanetta¹, Maxwell S Drexler², Isabel F Barton², Thomas J Zega^{1

3}

Affiliations

¹ Lunar and Planetary Laboratory, The University of Arizona,1629 E University Blvd, Tucson, AZ 85721, USA.
² Mining and Geological Engineering, The University of Arizona, 1235 James E. Rogers Way, Tucson, AZ 85719, USA.
³ Materials Science and Engineering, The University of Arizona, 1235 James E. Rogers Way, Tucson, AZ 85719, USA.

PMID: 37749720
DOI: 10.1093/micmic/ozac057

Abstract

We report on the electronic structure of vanadium in synthetic V-oxides and in natural roscoelite (V-rich phyllosilicate). This study applied electron energy-loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM), combined with first-principle calculations, to (1) establish relationships between the V oxidation state and EELS L2,3 features and (2) better constrain the oxidation state and crystallographic siting of V in roscoelite, with implications for other V-bearing phyllosilicates. Both EELS measurements and band structure calculations show that the EELS L2/L3 ratio increases as the oxidation state of V increases. We establish a quantitative relationship between the V L2,3 near-edge structure and the V oxidation state by normalizing the L2 maximum peak intensity to the L3 peak intensity. By applying this method to roscoelite, we find that it hosts a mix of trivalent and tetravalent V distributed between the octahedral and tetrahedral sites with a V4+/ΣV = 0.6 ± 0.1. This relationship is applicable to measurements of V oxidation states in oxide and phyllosilicate minerals, which is useful for constraining the conditions of rock and mineral formation and has potential implications for metal extraction from phyllosilicate ores.

Keywords: DFT calculations; STEM-EELS; V oxidation state; site occupancy; vanadium.