Chemical-Pressure-Induced Point Defects Enable Low Thermal Conductivity for Mg2Sn and Mg2Si Single Crystals

The development of thermoelectric (TE) materials, which can directly convert waste heat into electricity, is vital to reduce the use of fossil fuels. Mg2Sn and Mg2Si 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 Mg2Sn and Mg2Si 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 Mg2Sn and Mg2Si SCs were investigated. The B-doping increased the chemical pressure on the Mg2Sn and Mg2Si SCs, leading to inducing 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 high TE performance for the Mg2Sn and Mg2Si SCs.

Automated summary

This study applied boron doping to Mg2Sn and Mg2Si single crystals for point defect engineering, revealing that B-doping increased the chemical pressure and induced vacancy defects, significantly impeding thermal transport and providing a new approach for enhancing TE performance.