Sustainable and Simple Processing Technique for N-Type Skutterudites with High ZT and Their Analysis
Sustainable and Simple Processing Technique for N-Type Skutterudites with High ZT and Their Analysis
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DOI：
10.1016/j.actamat.2019.04.025
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发表时间：
2019-03
期刊：
影响因子：
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通讯作者：
G. Rogl;K. Yubuta;M. Kerber;A. Grytsiv;M. Zehetbauer;E. Bauer;P. Rogl
中科院分区：
文献类型：
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作者：
G. Rogl;K. Yubuta;M. Kerber;A. Grytsiv;M. Zehetbauer;E. Bauer;P. Rogl
由于工业的各个分支都对良好的热电发电机感兴趣，因此迫切需要一种简单，快速，廉价和可持续的优质热电材料生产路线。在本文中，我们演示了如何实现高ZT（ZT在823 K时为1.45）n型块状方钴矿，（Mm，Sm）yCo4Sb12，通过处理工业生产的原料粉末，使用改进的高压扭转（HPT）设备，在高温下，在惰性气体。对于这种HPT处理的样品以及退火的样品，结构特性，特别是集中在晶粒尺寸和位错密度上，（通过电子探针显微分析，透射电子显微镜调查以及XPD轮廓分析支持），物理性质（从300至823 K，电阻率另外从4.2至300 K）和机械性能（弹性模量、硬度、抗断裂性）进行测量和评估，并与传统制备的块状材料的值进行比较，使用热压（HP）。作为严重的塑性变形的结果，我们发现从金属到半导体的行为在测量诱导退火的HPT处理的方钴矿，这可以解释通过晶格畸变的变化及其对带隙的影响。出现了正的ZT净效应，因为虽然电阻率增加，但热导率降低。结果表明，HPT样品的弹性模量与HP方钴矿相差不大，但硬度明显增加。
As various branches of industry are interested in good thermoelectric generators, there is a serious demand for an easy, fast, cheap and sustainable production route of excellent thermoelectric materials. In this paper we demonstrate how we could achieve a high-ZT (ZT ∼ 1.45 at 823 K) n-type bulk skutterudite, (Mm,Sm)yCo4Sb12, by processing the industrially produced raw powder using a modified high-pressure torsion (HPT) equipment at elevated temperature under inert gas. For this HPT processed sample as well as for the annealed one, structural properties, especially focused on grain size and dislocation density (backed up by electron probe microanalysis, transmission electron microscopy investigations as well as XPD profile analysis), physical properties (from 300 to 823 K and for the electrical resistivity in addition from 4.2 to 300 K) and mechanical properties (elastic moduli, hardness, fracture resistance) were measured and evaluated and compared with the values of a traditionally prepared bulk material, using hot pressing (HP). As a consequence of severe plastic deformation, we found a change from metallic to semiconducting behavior during measurement induced annealing of the HPT processed skutterudite, which could be explained via the change of lattice distortion and its influence on the band gap. A positive ZT net effect occurred because although the electrical resistivity was enhanced the thermal conductivity was decreased. It turned out that the elastic moduli of the HPT samples were not much different from those of the HP skutterudite, however, that the hardness was significantly increased.