Chemical-pressure-induced point defects enable low thermal conductivity for MgSn and MgSi single crystals

化学圧力誘起点欠陥によるMgSnおよびMgSi単結晶の低熱伝導率化

齋藤 亘*; 林 慶*; Huang, Z.*; 杉本 和哉*; 大山 研司*; 八方 直久*; 原田 正英   ; 及川 健一   ; 稲村 泰弘  ; 林 好一*; 宮崎 孝道*; 宮崎 譲*

Saito, Wataru*; Hayashi, Kei*; Huang, Z.*; Sugimoto, Kazuya*; Oyama, Kenji*; Happo, Naohisa*; Harada, Masahide; Oikawa, Kenichi; Inamura, Yasuhiro; Hayashi, Koichi*; Miyazaki, Takamichi*; Miyazaki, Yuzuru*

The development of thermoelectric (TE) materials, which can directly convert waste heat into electricity, is vital to reduce the use of fossil fuels. MgSn and MgSi are promising TE materials because of their superior TE performance. In this study, for future improvement of the TE performance, point defect engineering was applied to the MgSn and MgSi single crystals (SCs) via boron (B) doping. Their crystal structures were analyzed via white neutron holography and SC X-ray diffraction. Moreover, nanostructures and TE properties of the B-doped MgSn and MgSi SCs were investigated. The B-doping increased the chemical pressure on the MgSn and MgSi SCs, leading to induce vacancy defects as a point defect. No apparent change was observed in electronic transport, but thermal transport was significantly prevented. This study demonstrates that the vacancy defects can be controlled by the chemical pressure, and can aid in achieving a high TE performance for the MgSn and MgSi SCs.