The Effect of High-Pressure Sintering Process on the Microstructure and Thermoelectric Properties of CoSb3

The high-pressure sintering process is studied for the fabrication of the bulk CoSb3 thermoelectric material. The CoSb3 powder is prepared by a solid reaction method, and then the samples are sintered under high-pressure conditions. The emphasis of the present study is on the influence of the pressure on the grain size and the electrical properties of the material. For the present study, the pressure is taken to be from 1.5 GPa to 6 GPa, and the sintering temperature is 723 K. The experimental results show that the major phase of skutterudite and traces of metal impurities of Sb and the CoSb2 phase coexist in some of the samples, and that the grain size of all the samples increase after sintering. In the range of 3.0 GPa to 6.0 GPa, the grain size increases with increasing pressure. In the range of 1.5 GPa to 3.0 GPa, the grain size also increases, but with a diminishing growth rate. All the materials show p-type transport behaviors, and the sample sintered under 2.0 GPa shows higher electrical conductivity than the 5.7 GPa sample, which may be due to the impurities.