Formation of Cerium-Filled Skutterudite Thermoelectric Materials in the Sintering of Gas-Atomized Powder

Abstract

A formation process of the CeFe 3 CoSb 12 thermoelectric materials with a filled skutterudite structure prepared using the gas atomized powder was studied. Fine powder particles were prepared by a fast Ar gas jet and characterized. It was found that these particles consist of the CeFe 3 CoSb 12 , FeSb 2 , FeSb and Sb. The differential scanning calorimetry curve indicates that thermoelectric materials were sintered through two exothermic reactions, i.e. the low temperature one probably corresponds to the oxidation of Sb and the high temperature one matches the skutterudite phase formation from latter three phases. Sintering conditions were adjusted in order to reduce the Sb oxidation and to ensure the skutterudite phase formation. As the result of thermoelectric measurements, the Seebeck coefficient increases, and the both electric conductivity and thermal conductivity decrease in the temperature range 300 850 K mainly with decreasing the residual Sb in the sintered materials. The maximum dimensionless figure of merit of 0.63 was obtained for the most improved specimen at 700 K.

Ce Filling Limit and Its Influence on Thermoelectric Performance of Fe3CoSb12-Based Skutterudite Grown by a Temperature Gradient Zone Melting Method

“…As can be seen, the Ce-filling level in the samples increases at first and then tends to be stabilized at the x of 1.25, which is consistent with the peak shift from XRD. prepared by different methods, including traditional melting (TM) for Ce0.2Fe0.1Co3.9Sb12, [58] arc melting (AM) for CeFe2Co2Sb12 [59] and CeFe0.75Co3.25Sb12 [39], gas-atomized powder sintering (GS) for CeFe3CoSb12, [45] scanning laser melting and spark plasma sintering (SS) for Ce0.95Fe3CoSb12.1 [46] and temperature gradient zone melting (TGZM) for this study.…”

“…The Fe3CoSb12 has a higher σ (1302 S cm −1 ) comparing with the Ce-filled samples in the entire measured temperature. With increasing the Ce-filling level, the σ of the CexFe3CoSb12 decreases from 1302 S cm −1 of the Fe3CoSb12 to 638 S cm −1 of the Ce1.25Fe3CoSb12 at 303 K. The slight increase of σ from x = 1.25 to 1.5 might be attributed to the slightly increased Sb content (as evi- [59] and CeFe 0.75 Co 3.25 Sb 12 [39], gas-atomized powder sintering (GS) for CeFe 3 CoSb 12 , [45] scanning laser melting and spark plasma sintering (SS) for Ce 0.95 Fe 3 CoSb 12.1 [46] and temperature gradient zone melting (TGZM) for this study. (d) Typical TEM-EDS spectrum of the CeFe 3 CoSb 12 .…”

“…Furthermore, charge-compensational doping by the substitution at Co or Sb sites has been widely applied to increase the filling faction of Ce in bulk CoSb 3 -based skutterudites, which can simultaneously tune n-type CoSb 3 skutterudites into p-type ones [43,44]. Tanahashi et al [45] found a Ce filling fraction of ~0.9 in p-type CoSb 3 -based skutterudites with the nominal composition of CeFe 3 CoSb 12 , which is prepared by gas-phase atomization and sintering and approached a zT of 0.63 at 700 K. Chen et al [46] reported a p-type Ce 0.95 Fe 3 CoSb 12.1 grown by scanning laser melting method combined with spark plasma sintering and achieved the Ce filling fraction of 0.85 and the zT of ~0.79 at 750 K.…”

“…Detailed component information acquired by EDS: (a) EDS spectra and corresponding (b) average atomic ratios of Fe, Co, Sb, Ce elements in CexFe3CoSb12 (x = 0 to 1.5) samples. (c) comparison of the Ce filling fraction in Fe-doped CoSb3 prepared by different methods, including traditional melting (TM) for Ce0.2Fe0.1Co3.9Sb12,[58] arc melting (AM) for CeFe2Co2Sb12[59] and CeFe0.75Co3.25Sb12[39], gas-atomized powder sintering (GS) for CeFe3CoSb12,[45] scanning laser melting and spark plasma sintering (SS) for Ce0.95Fe3CoSb12.1[46] and temperature gradient zone melting (TGZM) for this study. (d) Typical TEM-EDS spectrum of the CeFe3CoSb12.…”

“…Temperature-dependent (d) S 2 σ; (e) κ; (f) κe; (g) κl; (h) zT. (i) Comparison of the room-temperature κ for nominal Ce1.25Fe3CoSb12 with the reported values for CeFe2Co2Sb12 prepared by AM,[59] CeFe4Sb12[61] and Ce0.6Fe3CoSb12[62] prepared by TM, CeFe3CoSb12 prepared by GS,[45] Ce0.95Fe3CoSb12.1 prepared by SS,[46] and Ce0.86Fe3CoSb12.09 prepared by melt spinning and spark plasma sintering (MS)[63].…”