Abstract
One means of enhancing the performance of thermoelectric materials is to generate secondary nanoprecipitates of metallic or semiconducting properties in a thermoelectric matrix, to form proper band bending and, in turn, to induce a low-energy carrier filtering effect. However, forming nanocomposites is challenging, and proper band bending relationships with secondary phases are largely unknown. Herein, we investigate the in situ phase segregation behavior during melt spinning with various metal elements, including Ti, V, Nb, Mo, W, Ni, Pd, and Cu, in p-type Bi0.5Sb1.5Te3 (BST) thermoelectric alloys. The results showed that various metal chalcogenides were formed, which were related to the added metal elements as secondary phases. The electrical conductivity, Seebeck coefficient, and thermal conductivity of the BST composite with various secondary phases were measured and compared with those of pristine BST alloys. Possible band alignments with the secondary phases are introduced, which could be utilized for further investigation of a possible carrier filtering effect when forming nanocomposites.
Highlights
Thermoelectric technology has attracted attention for its use in solid-state cooling and energy harvesting because it can convert heat directly into electricity
The energy conversion efficiency of thermoelectric materials is limited by the dimensionless figure of merit, zT = [S2 ·σ/(κ ele + κ latt )] × T, where S is the Seebeck coefficient, σ is the electrical conductivity, κ ele is the electronic thermal conductivity, κ latt is the lattice thermal conductivity, and T is the absolute temperature [1,2,3,4]
When proper phase segregation is introduced in thermoelectric materials, the carrier energy filtering effect can be achieved, thereby enhancing the thermoelectric performance through low-energy carrier scattering by potential heights formed at heterointerfaces [13,14]
Summary
Thermoelectric technology has attracted attention for its use in solid-state cooling and energy harvesting because it can convert heat directly into electricity. Other strategies exist for reducing thermal conductivity These include inducing point defects, dislocation arrays, or nanostructures by increasing phonon scattering [9,10,11,12]. Of these approaches, carrier energy filtering can effectively improve zT by increasing. When proper phase segregation is introduced in thermoelectric materials, the carrier energy filtering effect can be achieved, thereby enhancing the thermoelectric performance through low-energy carrier scattering by potential heights formed at heterointerfaces [13,14]. Jiang et al reported noticeable maximum zT values of 1.56 at 400 K by inducing PbSe nanocomposites with suppressed lattice and bipolar thermal conductivities that effectively inhibit minor charge carriers [18]. The possible band alignments with secondary phases are presented with their measured thermoelectric properties
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