Thermoelectric Properties of In Situ Formed Bi0.85Sb0.15/Bi-Rich Particles Composite

Abstract

A Bi-15 at.%Sb alloy, homogenized by equal channel angular extrusion (ECAE) at T = 523 K, has been treated just above its solidus temperature, causing segregation of a secondary Bi-rich phase at the grain boundaries. This process results in an in situ composite. The thermoelectric properties of the composite have been measured in the range of 5 K < T < 300 K. The results are compared with those of the homogeneous alloy. The presence of a Bi-rich phase improves the Seebeck coefficient at T < 50 K, and enhances the electrical conductivity by a factor of 1.4 at T = 300 K up to a factor of 3.4 at T = 50 K; unfortunately, the thermal conductivity also increases by about 50% in the same temperature range. As a result, the figure of merit, Z, is slightly suppressed above T = 110 K, but increases at lower temperatures, reaching a peak value of 4.2 9 10 À3 K À1 at T = 90 K. The power factor considerably increases over the whole temperature range, rendering this material suitable as the n-type leg of a cryogenic thermoelectric generator for cold energy recovery in a liquefied natural gas plant.

Enhanced Figure of Merit in Bismuth-Antimony Fine-Grained Alloys at Cryogenic Temperatures

“…Typical methods used in previous studies relied mostly on the heat flow across the whole sample with multiple high thermal conductivity metal contact leads attached. Unsystematic variations of thermal conductivity data have been observed in measurements using PPMS, and previous studies by other groups relying on this type of measurement also reported a wide range of thermal conductivities 20,21,31,32 . This indicates there could be significant uncertainty associated with the thermal conductivity measurements due to radiative heat loss during the heating event or effects from metal contacts, especially for a low thermal conductivity system such as Bi-Sb.…”

Direct ink writing of high-performance Bi2Te3-based thermoelectric materials using quasi-inorganic inks and interface engineering

“…30 Since the pores among grain particles hinder the transportation of carriers, interface soldering by using liqueed phases can promote densication and electrical connection. 27,42,43 Te and Bi particles were introduced into p-and n-type Bi 2 Te 3 -based materials, and further printed, labeled p-type/Te and n-type/Bi, respectively. The detailed process can be seen in the Experimental section.…”

Thermal simulation of thermoelectric material by zone-melting technique

“…If the speed is too slow (0.6cm/hr) would cause the segregation of Te [6]. For p-type alloy, a homogeneous Bi-Sb alloy was treated for two minutes just above its melting temperature, causing segregation of Bi-rich phase at the grain boundaries, thus forming local inhomogeneities [7]. From the literature we can see the temperature gradient and the speed ratio (G / V) will affect the growth of crystal.…”