Low temperature thermoelectric properties of melt spun Bi85Sb15 alloys

Abstract

Single phase Bi85Sb15 bulk materials were prepared by a melt spinning (MS) combined with subsequent spark plasma sintering (SPS) technique (MS + SPS). The effects of cooling rate in MS process on the microstructure and low temperature thermoelectric properties (10–300 K) of bulk Bi85Sb15 have been systematically investigated. With increasing the cooling rate, the increase of constituents homogeneity and corresponding increase in actual energy gap give rise to a significant improvement of electron mobility and decrease in electron concentration, resulting in an optimized power factor with a highest value of 7.9 mW m K−2 for the sample with highest cooling rate. Meanwhile, the thermal conductivity retains a very low value due to the intensified phonon scattering by alloying and interfaces. Consequently, the sample with highest cooling rate exhibits a highest Z value of 2.74 × 10−3 K−1 at 120 K which is superior to most of polycrystalline sintered samples, mainly benefiting from its relatively higher power factor. In addition, the utilization of the rapid and energy-saving MS + SPS technique along with improved thermoelectric and mechanical performances is very promising for the cryogenic application of BiSb alloy.