Study On Preparation And Properties Of CoSb₃ Nanometer Thermoelectric Compounds

In order to make thermoelectric generation system practicable, high-performance thermoelectric material should be developed. At present, in all of the middle- temperature thermoelectric materials, PbTe is used the most widely but it has a severe pollution to environment. And its thermoelectric performance figure (ZTmax=0.9) is still very low. Therefore it is necessary to develop new type high-performance and environment friendly middle-temperature thermoelectric materials. As a type of potentially good thermoelectric materials, CoSb3 compounds with the skutterudite crystal structure MX3 have attracted attention widely, because of their high carrier mobility, large electrical conductivities, and large Seebeck coefficients. However, the thermal conductivity of skutterudite is too large, so, ZT is low. Therefore reducing the thermal conductivity of CoSb3 has becomed a main research way at present. In this research, nano-structure CoSb3 was prepared and its thermoelectric performance figure is better than micrometer structure CoSb3.CoSb3 micrometer powder has been synthesized by solid-state reaction. CoSb3 nano-powders were prepared by high-energy ball-milling respectively. The influence of mass ratio of big balls and small balls, milling speed and time on particles size of CoSb3 powder, were investigated. In appropriate conditions, CoSb3 powders with particles size of 50nm were prepared.CoSb3 nano-powders were used as starting materials, and bulk thermoelectric materials were prepared by Spark Plasma Sintering (SPS). We have investigated the influence of sintering temperature and sintering time on grains size. The results show that the grain size of CoSb3 grows with increasing sintering temperature or sintering time. When sintering temperature and sintering time are 625 C and 7min respectively, the densenfied bulk thermoelectric materials with mean grains size of 100nm were prepared.After testing thermal conductivity (K), electrical conductivity ( ) and See-beck coefficient (a), the results demonstrate that for CoSb3 nano-materials, withdecreasing in grains size lattice thermal conductivity falls, electrical conductivity decreases and Seebeck coefficient increases. Thermoelectric performance figure (ZT) CoSbs nano-compound with grains size of 200nm has reached 0.43.