Development of Ti-S-based n-type thermoelectric materials

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H04951
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Inorganic materials/Physical properties
• Research Institution: Kyushu University
• Principal Investigator: Koichiro Suekuni 九州大学, 総合理工学研究院, 准教授 (10582926)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 熱電材料 / 熱電物性 / チタン硫化物 / ゼーベック係数 / 出力因子 / 電子構造 / 半導体

Outline of Final Research Achievements

In this study, we aimed to develop novel n-type thermoelectric (TE) materials and to propose design guidelines for TE materials with excellent electronic properties. For the purpose, the TE properties and electronic structures were investigated for the materials with structural networks composed of edge-sharing TiS6 octahedra, namely Cu2Ti4S8 spinel and its related materials, layered materials (SnS)1.2(TiS2)n (n=1,2), and a quasi-one-dimensional material Sn1.2Ti0.8S3. N-type electronic properties arising from TiS6 network were observed for all the materials, for which the electron carrier concentration was tuned by elemental substitutions and oxidative extraction of Cu. As a result, TE figures of merit for the materials were enhanced. These results demonstrate that materials with TiS6 octahedral networks are promising as n-type TE materials. Furthermore, it was found that the substitution of Co for Ti in Cu2Ti4S8 was effective for improving electronic properties.

Free Research Field

熱電変換

Academic Significance and Societal Importance of the Research Achievements

熱電材料は未利用熱からの電力回収(熱電発電)への応用が期待されている。本研究では，チタンー硫黄系物質に着目し，その熱電物性を系統的に調べた。その結果，TiS6八面体の稜共有ネットワークを有する物質では，伝導帯を構成する電子軌道が類似すること，その電子構造がn型の電気的特性の発現に有利であることが判った。また，原子サイトへの空孔導入や元素置換などの方法により電子キャリア濃度を制御でき，熱電性能を高められることを確認した。得られた知見は，さらに高性能な熱電材料の開発に結び付くものと期待される。