Nanostructure Features, Phase Relationships and Thermoelectric Properties of Melt-Spun and Spark-Plasma-Sintered Skutterudites

Abstract

Reduction of thermal conductivity remains a main approach relevant to enhancement of figure-of-merit of most thermoelectric materials. Melt spinning combined with spark plasma sintering appears to be a vital route towards fine-grain skutterudites with improved thermoelectric performance. However, upon high-temperature processing the Fe4−xCoxSb12-based skutterudites are prone to decompose into multiple phases, which deteriorate their thermoelectric performance. In this study we addressed the effects of combined melt spinning and spark plasma sintering on the phase composition and microstructural properties of filled Fe4−xCoxSb12 as well as their influence on thermoelectric characteristics of these compounds. The crystallites of filled Fe4−xCoxSb12 were effectively reduced to sizes below 100 nm upon melt spinning, but also severe decomposition with weakly preserved nominal phase was observed. Spark plasma sintering of melt spun skutterudites resulted in even further reduction of crystallites. Upon short annealing and sintering the n-type materials easily restored into single-phase filled CoSb3 with nanoscale features preserved, while secondary phases of FeSb2 and Sb remained in p-type compounds. Relatively high figure-of-merit ZTmax of 0.9 at T ≈ 400•

A review of CoSb3-based skutterudite thermoelectric materials

“…It is not conducive to large-scale production and impedes the final commercial use of CoSb 3 -based TE materials for power generation. Therefore, some non-equilibrium preparation methods, such as melt spinning combined with spark plasma sintering (MS-SPS) [202][203][204], self-propagating high-temperature synthesis (SHS) method [205][206][207][208][209], and high pressure synthesis [66][67][68][69][70]210,211], have been adopted in recent years. Using these non-equilibrium preparation methods, the preparation period of the material was greatly shortened.…”