在块体材料中引入纳米组元构建微纳复合材料是热电材料研究的一个新方向. 采用原位溶剂热和热压方法制备了由纳米晶粒和微米晶粒组成的n 型CoSb3复合材料. 以CoCl2、SbCl3为原料, NaBH4为还原剂, 乙醇为溶剂, 与熔炼制备的n型CoSb3微米级别的粉末一起放入高压反应釜中, 在250℃下反应72h得到微纳复合的粉末材料, 热压后得到微纳复合的块体材料. 性能测试结果表明, 该材料表现为典型掺杂半导体的导电特征, 具有较好的电学性能. 微纳复合结构引入大量晶界增强了声子散射, 能有效降低材料的热导率, 并且由纳米组元引起的量子效应能提高材料的Seebeck系数, 使材料的热电性能得到改善. 本工作所制备的微纳复合n型CoSb3具有较低的热导率, 在测试温度范围内, 热导率为2.0～2.3W·m-1·K-1. 材料的最大无量纲热电优值在600K时达到0.5.
Nanocomposite structure is one of the promising directions towards advanced bulk thermoelectric materials. An n-type CoSb3 nanocomposite consisting nano- and micro-sized grains was prepared by in~situ solvothermal synthesis and hot pressing. Using CoCl2 and SbCl3 as precursors, NaBH4 as reductant, and ethanol as solvent, the start materials together with micro-grained n-type CoSb3 powders prepared by melting/annealing method were put into an autoclave and reacted at 250℃ for 72h. The bulk nanocomposite was prepared by hot pressing the as-synthesized products. The introduction of nanocomposite structure can reduce the thermal conductivity efficiently by interface scattering and increase the Seebeck coefficient by quantum confinement due to the nanoscale constituents, thereby improve the thermoelectric performance. It is shown that the composite has a doped semicondoctor behavior with good electrical properties. The phonon scattering is efficiently enhanced by the composite micro-/nano-structure, which reduces the thermal conductivity to 2.0-2.3W·m-1·K-1 in the nanocomposite. The highest dimensionless figure of merit obtained in the present work reaches 0.5 at 600K.
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