Microstructural analysis and thermoelectric properties of skutterudite CoSb3 materials produced by melt spinning and spark plasma sintering

Skutterudite CoSb3 thermoelectric materials were synthesized by a combination of melt spinning (MS) and consolidation by spark plasma sintering (SPS). Microstructural analysis was carried out on the MS-SPS samples using various analytical techniques such as XRD, SEM, EBSD and DSC/TGA. In the melt-spun ribbons, the initial microstructure consisted of a multiphase mixture of Sb and CoSbx (x = 1, 2, or 3) where CoSb3 is the only thermoelectric phase. Subsequent SPS processing caused conversion of other phases present (Sb, CoSb and CoSb2) into single-phase CoSb3 and recrystallization concurrently. The phase conversion mechanism has been explained in the present work using a thermodynamic interpretation. Thermoelectric transport measurement results show that the thermal conductivity of MS-SPS sample was significantly decreased as compared with that of the sample prepared by traditional methods combined with SPS (TM-SPS) due to the reduction of its grain size. Compared with TM-SPS sample, MS-SPS sample has a high ZT value at room temprerature because of its high electrical conductivity and low lattice thermal conductivity.