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An EPR Investigation of defect structure and electron transfer mechanism in mixed-conductive LiBO2-V2O5 glasses

Spencer, Jacob N., Folli, Andrea, Ren, Hong and Murphy, Damien M. 2021. An EPR Investigation of defect structure and electron transfer mechanism in mixed-conductive LiBO2-V2O5 glasses. Journal of Materials Chemistry A: materials for energy and sustainability 9 (31) , pp. 16917-16927. 10.1039/D1TA02352G

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Abstract

Continuous Wave (CW) Electron Paramagnetic Resonance (EPR) spectroscopy was used to study the defect structure and electron transfer mechanism in a series of LiBO2-V2O5 mixed conductive glasses of varying V2O5 content. These glassy materials are attracting growing interest for energy storage devices. At low V2O5 content (VLB1), an isolated S = ½ vanadium defect centre is found at a network modifying position within the LiBO2 matrix. The observed spin Hamiltonian parameters are consistent with a V4+ centre possessing a distorted octahedral configuration and dxy orbital ground state. At high V2O5 content (VLB3), the vanadium hyperfine structure is absent indicative of a distinct exchange-narrowed signal. A model was developed to analyse the linewidth and g-tensor component of the EPR signals, revealing a marked temperature dependent behaviour, consistent with a polaron hopping mechanism of electron transfer and inter-electronic exchange along the g3 direction, coincident with the electron transfer axis. The activation energy (Ea) was estimated to be 0.0805 eV, consistent with other conducting glasses. A relaxation-dominated line broadening mechanism was further supported by multi-frequency EPR measurements, which also identified unresolved features at high frequencies due to unaccounted for anisotropic exchange / speciation within the disordered network. This analysis provides a straight-forward method for the use of EPR to investigate solid-state glassy materials.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Additional Information: This article is licensed under a Creative Commons Attribution 3.0 Unported Licence
Publisher: Royal Society of Chemistry
ISSN: 2050-7488
Funders: EPSRC and Johnson Matthey
Date of First Compliant Deposit: 26 July 2021
Date of Acceptance: 20 July 2021
Last Modified: 15 Sep 2021 12:25
URI: http://orca.cardiff.ac.uk/id/eprint/142880

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