Mao Jun, Wang Yumei, Ge Binghui, Jie Qing, Liu Zihang, Saparamadu Udara, Liu Weishu, Ren Zhifeng
Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, TX 77204, USA.
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China.
Phys Chem Chem Phys. 2016 Jul 27;18(30):20726-37. doi: 10.1039/c6cp03944h.
In this study, the thermoelectric properties of Mg2Sn0.98-xPbxSb0.02 were first studied, and then Mg2Sn0.93-xSixPb0.05Sb0.02 and Mg2Sn0.93-xGexPb0.05Sb0.02 were accordingly investigated. The results showed that the formation of Mg2Sn0.98-xPbxSb0.02 solid solutions effectively reduced the lattice thermal conductivity of Mg2Sn. The room temperature lattice thermal conductivity of Mg2Sn0.98Sb0.02 is ∼5.2 W m(-1) K(-1) but only ∼2.5 W m(-1) K(-1) for Mg2Sn0.73Pb0.25Sb0.02, a reduction of ∼52%. Further alloying Mg2Sn0.98-xPbxSb0.02 with Mg2Si or Mg2Ge to form Mg2Sn0.93-xSixPb0.05Sb0.02 or Mg2Sn0.93-xGexPb0.05Sb0.02 reduced the lattice thermal conductivity significantly due to enhanced phonon scattering by point defects as well as nanoparticles. Moreover, bipolar thermal conductivities were suppressed due to the larger bandgap of Mg2Si and Mg2Ge than Mg2Sn. Furthermore, similar to the pseudo-binary Mg2Sn-Mg2Si and Mg2Sn-Mg2Ge systems, band convergence was also observed in pseudo-ternary Mg2Sn0.93-xSixPb0.05Sb0.02 and Mg2Sn0.93-xGexPb0.05Sb0.02 materials. The convergence of conduction bands led to higher PFs at lower temperatures for Mg2Sn0.93-xSixPb0.05Sb0.02 and Mg2Sn0.93-xGexPb0.05Sb0.02 materials. As a result, higher peak ZTs of ∼1.3 for Mg2Sn0.63Si0.3Pb0.05Sb0.02 and ∼1.2 for Mg2Sn0.68Ge0.25Pb0.05Sb0.02 were achieved.
在本研究中，首先对Mg2Sn0.98-xPbxSb0.02的热电性能进行了研究，随后相应地对Mg2Sn0.93-xSixPb0.05Sb0.02和Mg2Sn0.93-xGexPb0.05Sb0.02进行了研究。结果表明，Mg2Sn0.98-xPbxSb0.02固溶体的形成有效降低了Mg2Sn的晶格热导率。Mg2Sn0.98Sb0.02的室温晶格热导率约为5.2 W m(-1) K(-1)，而Mg2Sn0.73Pb0.25Sb0.02仅约为2.5 W m(-1) K(-1)，降低了约52%。进一步将Mg2Sn0.98-xPbxSb0.02与Mg2Si或Mg2Ge合金化以形成Mg2Sn0.93-xSixPb0.05Sb0.02或Mg2Sn0.93-xGexPb0.05Sb0.02，由于点缺陷以及纳米颗粒增强了声子散射，显著降低了晶格热导率。此外，由于Mg2Si和Mg2Ge的带隙比Mg2Sn大，双极热导率受到抑制。此外，类似于伪二元Mg2Sn-Mg2Si和Mg2Sn-Mg2Ge体系，在伪三元Mg2Sn0.93-xSixPb0.05Sb0.02和Mg2Sn0.93-xGexPb0.05Sb0.02材料中也观察到了能带收敛。导带的收敛导致Mg2Sn0.93-xSixPb0.05Sb0.02和Mg2Sn0.93-xGexPb0.05Sb0.02材料在较低温度下具有更高的功率因子。结果，Mg2Sn0.63Si0.3Pb0.05Sb0.02实现了约1.3的更高峰值ZT，Mg2Sn0.68Ge0.25Pb0.05Sb0.02实现了约1.2的更高峰值ZT。
