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Y2Ti2O5S2 – a promising n-type oxysulphide for thermoelectric applications

Brlec, Katarina; Spooner, Kieran B; Skelton, Jonathan M; Scanlon, David O; (2022) Y2Ti2O5S2 – a promising n-type oxysulphide for thermoelectric applications. Journal of Materials Chemistry A 10.1039/d2ta04160j. (In press). Green open access

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Abstract

Thermoelectric materials offer an unambiguous solution to the ever-increasing global demand for energy by harnessing the Seebeck effect to convert waste heat to electrical energy. Mixed-anion materials are ideal candidate thermoelectric materials due to their thermal stability and potential for “phonon-glass, electron-crystal” behaviour. In this study, we use density-functional theory (DFT) calculations to investigate Y2Ti2O5S2, a cation-deficient Ruddlesden-Popper system, as a potential thermoelectric. We use hybrid DFT to calculate the electronic structure and band alignment, which indicate a preference for n-type doping with highly anisotropic in-plane and the out-of-plane charge-carrier mobilities as a result of the anisotropy in the crystal structure. We compute phonon spectra and calculate the lattice thermal conductivity within the single-mode relaxation-time approximation using lifetimes obtained by considering three-phonon interactions. We also calculate the transport properties using the momentum relaxation-time approximation to solve the electronic Boltzmann transport equations. The predicted transport properties and lattice thermal conductivity suggest a maximum in-plane ZT of 1.18 at 1000 K with a carrier concentration of 2.37 × 1020 cm−3. Finally, we discuss further the origins of the low lattice thermal conductivity, in particular exploring the possibility of nanostructuring to lower the phonon mean free path, reduce the thermal conductivity, and further enhance the ZT. Given the experimentally-evidenced high thermal stability and the favourable band alignment found in this work, Y2Ti2O5S2 has the potential to be a promising high-temperature n-type thermoelectric.

Type: Article
Title: Y2Ti2O5S2 – a promising n-type oxysulphide for thermoelectric applications
Open access status: An open access version is available from UCL Discovery
DOI: 10.1039/d2ta04160j
Publisher version: https://doi.org/10.1039/D2TA04160J
Language: English
Additional information: © 2022 The Authors. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/)
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL
URI: https://discovery.ucl.ac.uk/id/eprint/10152377
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