| Institution: | 1. Department of Materials Science and Engineering, and Institute of Materials Genome & Big Data, Harbin Institute of Technology, Shenzhen, Guangdong, 518055 P. R. China;2. School of Science, Harbin Institute of Technology, Shenzhen, Guangdong, 518055 P. R. China;3. Ningbo Fengcheng Advanced Energy Materials Research Institute, Fenghua District, Ningbo, Zhejiang, 315500 China;4. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin, Heilongjiang, 150001 P. R. China;5. Department of Materials Science and Engineering, and Institute of Materials Genome & Big Data, Harbin Institute of Technology, Shenzhen, Guangdong, 518055 P. R. China
State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin, Heilongjiang, 150001 P. R. China;6. Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX, 77204 USA |
| Abstract: | The 19-electron VCoSb compounds are actually composites of an off-stoichiometric half-Heusler phase and impurities. Here the compositional adjustment is systematically studied in V1−xCoSb to obtain single-phase V0.955CoSb. Hall measurements suggest that such a V vacancy, as well as Ti doping, can optimize the carrier concentration, which decreases from ≈11.3 × 1021 cm−3 for VCoSb to ≈6.3 × 1021 cm−3 for V0.755Ti0.2CoSb. Low sound velocity contributes to the intrinsically low lattice thermal conductivity for VCoSb-based materials. The high Ti-dopant content results in enhanced point-defect scattering, which further decreases the lattice thermal conductivity. Finally, the optimized n-type V0.855Ti0.1CoSb is found to reach a peak ZT of ≈0.7 at 973 K. The work demonstrates that the VCoSb-based half-Heuslers are promising thermoelectric materials. |
