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首页> 外文会议>Nanoscale thermoelectric materials: Thermal and electrical transport, and applications to solid-state cooling and power generation >Enhanced Thermoelectric Figure-of-merit at Room Temperature in Bulk Bi(Sb)Te(Se) With Grain Size of～100nm
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Enhanced Thermoelectric Figure-of-merit at Room Temperature in Bulk Bi(Sb)Te(Se) With Grain Size of～100nm

机译：晶粒尺寸〜100nm的Bi（Sb）Te（Se）体在室温下的增强热电品质因数

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摘要

Grain boundaries are known to be able to impede phonon transport in the material. In the thermoelectric application, this phenomenon could help improve the figure-of-merit (ZT) and enhance the thermal to electrical conversion. Bi_2Te_3 based alloys are renowned for their high ZT around room temperature but still need improvements, in both n- and p-type materials, for the resulting power generation devices to be more competitive. To implement high density of grain boundaries into the bulk materials, a bottom-up approach is employed in this work: consolidations of nanocrystalline powders into bulk disks. Nanocrystalline powders are developed by high energy cryogenic mechanical alloying that produces Bi(Sb)Te(Se) alloy powders with grain size in the range of 7 to 14 nm, which is about 25% finer compared to room temperature mechanical alloying. High density of grain boundaries are preserved from the powders to the bulk materials through optimized high pressure hot pressing. The consolidated bulk materials have been characterized by X-ray diffraction and transmission electron microscope for their composition and microstructure. They mainly consist of grains in the scale of 100 nm with some distributions of finer grains in both types of materials. Preliminary transport property measurements show that the thermal conductivity is significantly reduced at and around room temperature: about 0.65 W/m-K. for the n-type BiTe(Se) and 0.85 W/m-K for the p-type Bi(Sb)Te, which are attributed to increased phonon scattering provided by the nanostructure and therefore enhanced ZT about 1.35 for the n-type and 1.21 for the p-type are observed. Detailed transport properties, such as the electrical resistivity, Seebeck coefficient and power factor as well as the resulting ZT as a function of temperature will be described.
机译：已知晶界能够阻止声子在材料中的传输。在热电应用中，这种现象可以帮助改善品质因数（ZT）并增强热电转换。基于Bi_2Te_3的合金因其在室温下的高ZT而闻名，但仍需要对n型和p型材料进行改进，以使发电设备更具竞争力。为了在散装材料中实现高密度的晶界，这项工作采用了一种自下而上的方法：将纳米晶体粉末固结到散装盘中。纳米晶体粉末是通过高能低温机械合金化技术开发的，该技术可生产出晶粒尺寸为7至14 nm的Bi（Sb）Te（Se）合金粉末，与室温机械合金化相比，其细度约为25％。通过优化的高压热压，可以保持从粉末到块状材料的高晶界密度。固结的散装材料已经通过X射线衍射和透射电子显微镜对其组成和微观结构进行了表征。它们主要由100 nm尺度的晶粒组成，在两种材料中都有一些较细的晶粒分布。初步的运输性能测量表明，在室温及其附近，导热系数显着降低：约0.65 W / m-K。对于n型BiTe（Se）而言，对于P型Bi（Sb）Te而言，为0.85 W / mK，这归因于纳米结构提供的声子散射增加，因此，对于n型BiTe（Se）而言，ZT增强了1.35，对于Z型而言，ZT增强了1.21。观察到p型。将描述详细的传输特性，例如电阻率，塞贝克系数和功率因数以及所得的ZT与温度的关系。

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