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以平均晶粒尺寸约3μm及20nm的Mg2Si粉末为原料,采用放电等离子体烧结方法制备出不同纳米、微米含量的Mg2Si纳微米复合块体材料,系统研究了纳微米结构对材料热电性能的影响。结果表明:随复合材料中纳米颗粒含量的增加,晶界散射增强,导致材料晶格热导率κp有明显降低;同时晶界势垒散射的增强也导致Seebeck系数α显著增加,电导率σ有一定程度的降低;综合Seebeck系数α、电导率σ、热导率κ的影响,在纳米颗粒含量为50%(质量分数,下同)、823K时,获得最大热电优值达0.45,分别是未掺杂纳米相和完全纳米相Mg2Si材料的1.5及1.1倍。纳微米复合结构的引入,可以获得性能更好的Mg2Si热电材料。
The Mg2Si nanocomposite materials with different nanometer and micron content were prepared by spark plasma sintering method using Mg2Si powder with average grain size of about 3μm and 20nm as raw materials. The effects of nanometer structure on the thermoelectric properties were investigated systematically. The results show that with the increase of the content of nano-particles in the composite, the grain boundary scattering increases, resulting in a significant decrease of the lattice thermal conductivity κp. At the same time, the enhancement of the barrier-scattering at the grain boundary also leads to a significant increase of the Seebeck coefficient α, A certain degree of reduction; the Seebeck coefficient α, the conductivity σ, the thermal conductivity κ, the maximum pyrolytic merit reaching 0.45 at the nanoparticle content of 50% (mass fraction, the same below) and 823K, respectively 1.5 and 1.1 times more doped nanophase and completely nanophase Mg2Si material. The introduction of nano-micron composite structure, you can get better performance Mg2Si thermoelectric materials.