Mg_2Si同质纳微米复合材料的制备及其热电性能

以平均晶粒尺寸约3μm及20 nm的Mg_2Si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Mg_2Si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κ_p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)、823 K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Mg_2Si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Mg_2Si热电材料.

Preparation and Thermoelectric Properties of Mg_2Si Nano-/Micro composites

Mg_2Si nanocomposites were prepared by spark plasma sintering (SPS) of the mixture of nanoscale and microsized Mg_2Si powder obtained by mechanical milling and solid-state reaction, respectively. Microstructure analysis shows that the bulk materials are composed of nano- and micrograins. The increase of nanosized powders is effective in reducing thermal conductivity, electrical conductivity and increasing Seebeck coefficient α. Taking the thermal conductivity, Seebeck coefficient and electrical conductivity into consideration, a maximum dimensionless figure of merit of 0.45 is obtained for the nanocomposite with 50wt % nanopowder inclusions at 823 K, about 1.5 times and 1.1 times higher than that of samples with 0wt% and 100wt% nanopowder inclusions, respectively. It could be expected that the properties of the nanocomposites could be further improved by doping optimization.