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

Abstract

The high-pressure sintering process is studied for the fabrication of the bulk CoSb 3 thermoelectric material. The CoSb 3 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 CoSb 2 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.

Impact of high pressure torsion on the microstructure and physical properties of Pr0.67Fe3CoSb12, Pr0.71Fe3.5Ni0.5Sb12, and Ba0.06Co4Sb12

“…Besides that, there are some state-of-art deformation methods producing nanostructured materials from bulk to bulk directly. For Ce 0.29 Fe 1.4 Co 2.6 Sb 11.24 uniaxial compression has been used under 150 MPa up to 20 cycles [14], for CoSb 3 high pressure sintering at 723 K in a pressure range from 2 to 6 GPa [15], and for Co 4 Sb 12−x Te x also high pressure sintering at 900 K under 1.5 GPa [16]. Recently, however, the new methods of severe plastic deformation have been applied, also for preparation of thermoelectric materials, for instance, equal channel angular extrusion (ECAE) [17][18][19][20][21] and high pressure torsion (HPT) [22,23] for preparation of bismuth telluride based compounds.…”

Synthesis Optimization and Thermoelectric Properties of S-Filled and Te-Se Double-Substituted Skutterudite under High Pressure

“…The pressure for synthesizing skutterudite using the HPHT method is in the range of 1.5–3.0 GPa, and the volume activity energy is negative; thus, in the above pressure range, the pressure inhibits the grain growth. When the synthesis pressure is 3.5 GPa, the activation volume is positive, and the pressure promotes the growth of grain size . Therefore, the grain size of the samples synthesized under the condition of 3.5 GPa is larger than that of the samples synthesized at 3.0 GPa.…”

“…When the synthesis pressure is 3.5 GPa, the activation volume is positive, and the pressure promotes the growth of grain size. 26 Therefore, the grain size of the samples synthesized under the condition of 3.5 GPa is larger than that of the samples synthesized at 3.0 GPa. If the crystal growth process is governed by point defects in thermal equilibrium, ΔV* is the sum of ΔV f and ΔV m .…”