Rapid Preparation of Intrinsic CoSb3 Thermoelectric Skutterudites by Modulating Peritectic Solidification

CoSb 3 -based thermoelectric materials exhibit excellent potential for waste heat recovery applications, but the conventional solidification and annealing process has limited their efficient fabrication. Here, a rapid and efficient method for preparing CoSb 3 skutterudite was proposed by combining liquid undercooling with isothermal solidification technique. Liquid Co 25 Sb 75 alloy was initially undercooled below its liquidus temperature by glass fluxing method to refine primary CoSb microstructures. The remarkably increased number of CoSb grains served as the nucleation sites for CoSb 2 phase during subsequent peritectic solidification, thereby indirectly promoting the grain refinement of the final peritectic CoSb 3 phase. The enhancement of liquid undercooling facilitated the formation of both CoSb 2 and CoSb 3 peritectic phases, resulting in a drastically increased volume fraction of CoSb 3 by a brief isothermal holding at its actual nucleation temperature. Electron backscatter diffraction (EBSD) characterization revealed that the average grain size of final CoSb 3 phase decreased from 16.5 to 3.29 μm as liquid undercooling increased from 5 to 126 K. A 15-minute isothermal holding at the actual nucleation temperature of CoSb 3 could enhance its volume fraction from 23% (without isothermal holding) to more than 97%. This procedure of high undercooling coupled with isothermal holding at the second peritectic reaction temperature brought in a zT value rise of 25 times for the intrinsic CoSb 3 phase.