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.
| Original language | English |
|---|---|
| Pages (from-to) | 16813-16824 |
| Number of pages | 12 |
| Journal | Journal of Materials Chemistry A |
| Volume | 10 |
| Issue number | 32 |
| Early online date | 4 Jul 2022 |
| DOIs | |
| Publication status | Published - 28 Aug 2022 |
Bibliographical note
Acknowledgements:KB, KBS and DOS acknowledge support from the European Research Council, ERC (grant no. 758345). We are grateful to the UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by EPSRC (EP/P020194/1 and EP/T022213/1) and to UCL for the provision of the Kathleen (Kathleen@UCL) and Myriad (Myriad@UCL) supercomputers. DOS acknowledges support from the EPSRC (EP/N01572X/1). DOS acknowledges membership of the Materials Design Network. Via our membership of the UK HEC Materials Chemistry Consortium, which is funded by the UK Engineering and Physical Sciences Research Council (EP/R029431), this work used the ARCHER2 UK National Supercomputing Service (https://www.archer2.ac.uk). JMS is currently supported by a UK Research and Innovation Future Leaders Fellowship (MR/T043121/1), and previously held a University of Manchester Presidential Fellowship.