Synthesis routes of CoSb3 need a long reaction time, especially at high temperature and-/or high pressure. Although the modified polyol process assisted with microwave radiation can be used to solve these problems, it used the excess amount of Sb ion. Therefore, this study aimed to solve this drawback by retarding the rate of reduction. The different microwave times (0, 1, and 3 min) were investigated to find out the shortest heating duration for preparing CoSb3 nanoparticles. Te-doped and Sn-doped CoSb3 were synthesized to investigate the benefit of this synthesis method for increasing the solubility limit of Te and Sn in the CoSb3 structure. The phase and microstructure of the synthesized products were characterized by using x-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the high crystalline phase of CoSb3 (JCPDS: 78-0977) without any metallic impurity phases product was successfully synthesized in 3 minutes for a heating time at normal pressure, non-excessive addition of Sb ion precursor, and low temperature. The XRD results of Te-doped and Sn-doped CoSb3 products exhibited poor crystalline phase and hard to exactly identify. In SEM and TEM results, the CoSb3 powder consisted of very tiny spherical-like particles around 10 nanometers attaching together even at different microwave time similar to Te-doped/Sn-doped samples.
The efficient strategies to minimize thermal conductivity in skutterudite materials are creating point defects along with nanosized grains. In this report, Sn and Se co-doped CoSb3 materials were synthesized through mixed-ball milling and spark plasma sintering techniques to utilize this strategy. Their phases, microstructure and thermoelectric properties were investigated under the content variation of Sn and Se in CoSb3 samples. The experimental results revealed that the Sn and Se were substituted at Sb sites in CoSb3 crystal structure and grain sizes were restricted to a hundred nanometer. The lattice thermal conductivity was reduced to 2.4[Formula: see text]W/mK at 298K. Interestingly, increasing Sn and Se doped content could further minimize the lattice thermal conductivity. The lowest value at room temperature is 1.79[Formula: see text]W/mK for CoSb[Formula: see text]Sn[Formula: see text]Se[Formula: see text] which was dramatically lower than pure CoSb3. Moreover, the increment of Sn and Se content also increased the electrical conductivity of doped samples, while the negative Seebeck coefficient sign tended to decrease. As expected, low electrical conductivity and substantial reduction in the Seebeck coefficient of doped samples at high measurement temperature, resulting in low power factor and low ZT values. It was clearly seen that the highest power factor of 880[Formula: see text][Formula: see text]W/mK2 was found at 516[Formula: see text]K in CoSb[Formula: see text]Sn[Formula: see text]Se[Formula: see text]. Furthermore, it also dominated the highest ZT value of 0.29 at 565 K, compared to the other Sn and Se co-doped samples. From these results, ball milling under dry conditions followed by wet conditions not only allowed a longer milling process but also generated a small fraction of pore which was a part of the reduction in thermal conductivity. Especially, the advantage of the existence of Sn and Se point defects and nanosized grains from this work will be escalated when it was applied to prepare materials that have high power factor values.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.