Back Song Yi, Yun Jae Hyun, Cho Hyunyong, Kim Gareoung, Rhyee Jong-Soo
Department of Applied Physics, Integrated Education Institute for Frontier Science and Technology (BK21 Four) and Institute of Natural Sciences, Kyung Hee University, Yongin 17104, Korea.
Energy Materials Laboratory, Toyota Technological Institute, Nagoya 468-8511, Japan.
Materials (Basel). 2021 May 12;14(10):2506. doi: 10.3390/ma14102506.
Bismuth-Telluride-based compounds are unique materials for thermoelectric cooling applications. Because BiTe is a narrow gap semiconductor, the bipolar diffusion effect is a critical issue to enhance thermoelectric performance. Here, we report the significant reduction of thermal conductivity by decreasing lattice and bipolar thermal conductivity in extrinsic phase mixing of MgO and VO nanoparticles in BiSbTe (BST) bulk matrix. When we separate the thermal conductivity by electronic κel, lattice κlat, and bipolar κbi thermal conductivities, all the contributions in thermal conductivities are decreased with increasing the concentration of oxide particle distribution, indicating the effective phonon scattering with an asymmetric scattering of carriers. The reduction of thermal conductivity affects the improvement of the values. Even though significant carrier filtering effect is not observed in the oxide bulk composites due to micro-meter size agglomeration of particles, the interface between oxide and bulk matrix scatters carriers giving rise to the increase of the Seebeck coefficient and electrical resistivity. Therefore, we suggest the extrinsic phase mixing of nanoparticles decreases lattice and bipolar thermal conductivity, resulting in the enhancement of thermoelectric performance over a wide temperature range.
基于铋碲的化合物是用于热电冷却应用的独特材料。由于BiTe是一种窄带隙半导体，双极扩散效应是提高热电性能的关键问题。在此，我们报道了通过在BiSbTe（BST）块体基质中外在相混合MgO和VO纳米颗粒来降低晶格热导率和双极热导率，从而显著降低热导率。当我们将热导率按电子热导率κel、晶格热导率κlat和双极热导率κbi进行区分时，随着氧化物颗粒分布浓度的增加，热导率的所有贡献都降低了，这表明存在与载流子不对称散射相关的有效声子散射。热导率的降低影响了优值的提高。尽管由于颗粒的微米级团聚，在氧化物块体复合材料中未观察到显著的载流子过滤效应，但氧化物与块体基质之间的界面会散射载流子，从而导致塞贝克系数和电阻率增加。因此，我们认为纳米颗粒的外在相混合降低了晶格热导率和双极热导率，从而在很宽的温度范围内提高了热电性能。
