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Reduction of lattice thermal conductivity (κlat) is one of the most critical strategies for achieving high thermoelectric energy conversion efficiency (ZT). SrTiO3 is regarded as an environmentally benign thermoelectric material. Complex cation-site defects in SrTiO3, such as those produced by heavy-mass rare-earth cation substitution and the formation of Sr vacancies, have been proven effective in reducing κlat. In this paper, we synthesized SrTiO3−x−δHxVOδ bulk polycrystals with complex anion-site defects, incorporating large amounts of both hydrogen anions (Hδ) and oxygen vacancies (VO), with the total concentration of x + δ controlled over a wide range from 0.16 to 0.40. As increasing x + δ values, κlat at 300 K largely decreased from 8.22 W/(mK) for pure SrTiO3 to 4.02 W/(mK) for SrTiO2.40H0.27VO0.13, which exhibited glass-like phonon transport. Both H and VO were found to contribute almost equally to phonon scattering, attributed to local structure distortions in Ti−O6 octahedra. In contrast, while the carrier activation rate of Hδ was nearly 100%, that of VO was only 23-27% in SrTiO3-x-δHxVOδ bulks, allowing the realization of low κlat and a high power factor (PF) even at high x + δ values. The highest ZT value of ~0.1 was obtained at 300 K for SrTiO2.73H0.16VO0.11, and further increased to 0.21 at 673 K for SrTiO2.60H0.27VO0.13. These findings demonstrate that anion-site defect engineering via mixed-anion substitution and vacancy formation is a promising strategy for further reducing K_lat and enhancing the performance of thermoelectric oxides.

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• In Copyright
  

  This document is the Accepted Manuscript version of a Published Work that appeared in final form in
  ACS Applied Energy Materials, copyright © 2025 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acsaem.5c01610.

Keyword: Thermoelectric material, Transition metal oxide, Hydrogen, Phonon transport, Carrier transport

Date published: 2025-08-11

Publisher: American Chemical Society (ACS)

Journal:

• ACS Applied Energy Materials (ISSN: 25740962) vol. 8 issue. 15 p. 11447-11455

Funding:

• Ministry of Education, Culture, Sports, Science and Technology JPMXP1122683430
• Murata Science and Education Foundation
• Japan Society for the Promotion of Science 24K21671
• Japan Society for the Promotion of Science JP20H00302
• Japan Society for the Promotion of Science JP21H04612
• Japan Society for the Promotion of Science JP22H01766
• Japan Society for the Promotion of Science JP22H04964
• Japan Society for the Promotion of Science JP22K18881
• Japan Society for the Promotion of Science JP24H00376
• Kanagawa Institute of Industrial Science and Technology
• Institute of Science Tokyo

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.5753

First published URL: https://doi.org/10.1021/acsaem.5c01610

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Updated at: 2025-09-11 09:06:08 +0900

Published on MDR: 2026-07-25 08:28:03 +0900