Ultra‐High Thermoelectric Performance in Bulk BiSbTe/Amorphous Boron Composites with Nano‐Defect Architectures

Abstract

trical conductivity, S is Seebeck coefficient, T is the absolute temperature, and κ is the thermal conductivity (κ = electronic (κ e) + lattice thermal conductivity (κ L)). [2,3] The state-of-the-art bismuth telluride-based thermoelectric (TE) materials have been used for refrigeration applications. [4] However, their ZT is limited to about 1 at room temperature, making such cooling devices less powerful and cost-competitive than other conventional technologies such as mechanical vapor-compression cooling systems. Further improving the ZT would facilitate their widespread application in industrial waste heat harvesting and electronic device cooling. [5] Maximizing ZT requires the enhancement of the power factor (PF = S 2 σ) and the reduction of thermal conductivity. [6,7] Several approaches have recently been implemented to enhance ZT, including improvement of PF by optimizing carrier concentration, [8-10] band convergence, [11,12] resonant levels, [13] energy barrier filtering, [14] and reducing κ L by alloying, [15] all-scale hierarchical architectures [16-18] and nanostructuring. [19-21] In particular, reduction of κ L by nanostructuring or through formation of nanocomposites has been demonstrated to be an effective Based on the Seebeck and Peltier effects, state-of-the-art bismuth telluridebased thermoelectric materials, which are capable of direct and reversible conversion of thermal to electrical energy, have great potential in energy harvesting and solid-state refrigerators. However, their widespread use is limited by their low conversion efficiency, which is determined by the dimensionless figure-of-merit (ZT). Significant enhancement of ZT is a great challenge owing to the common interdependence of electrical and thermal conductivity. Here, it is demonstrated that by incorporating nanoamorphous boron into the p-type Bi 0.5 Sb 1.5 Te 3 , a record high ZT of 1.6 at 375 K is achieved. It is shown that a high density of nanostructures and dislocations due to the incorporation of the boron inclusions, leads to a significant reduction of thermal conductivity and improved charge transport. The findings represent an important step to further promote the development of thermoelectric technology and its widespread application in solid-state refrigeration and power generation from waste heat.

Boron Strengthened GeTe‐Based Alloys for Robust Thermoelectric Devices with High Output Power Density

“…In this work, boron is introduced to strengthen GeTe, motivated by the positive role of boron on enhancing the TE or the mechanical properties of CoSb 3 ‐, [ 20 ] Bi 2 Te 3 ‐, [ 65 ] MgAgSb‐, [ 66 ] and Mg 3 Sb 2 ‐based compounds, [ 67 ] though TE devices were not considered in previous studies. We find that boron acts as an interfacial tailor to simultaneously improve the mechanical and TE performance of GeTe‐based alloys.…”

Weighted Mobility Ratio Engineering for High‐Performance Bi–Te‐Based Thermoelectric Materials via Suppression of Minority Carrier Transport

“…A significantly enhanced zT in Bi-Sb-Te by introduction of nanoamorphous boron might also be related to the increase of A. [51] It is to be noted that the variation in n H by the introduction of defect structures should be compensated to obtain maximum zT.…”

“…An increase in A was demonstrated with Bi-Sb-Te nanograined bulk in this study; however, it is not limited to Bi-Te or nanograined materials. Indeed, the A of any thermoelectric materials can be controlled by introducing multiscale defects (e.g., 0D point defects, [49] 1D dislocations, [10] 2D boundaries, [50] and 3D inclusions [51] ). A significantly enhanced zT in Bi-Sb-Te by introduction of nanoamorphous boron might also be related to the increase of A.…”

Current State‐of‐the‐Art in the Interface/Surface Modification of Thermoelectric Materials

“…Among the several types of second phases that have been incorporated into TE materials to enhance their zT value, silicon carbide nanoparticles have attracted significant interest. Many semiconductors, such as SiC, [ 131–142 ] MgB 2 , [ 143,144 ] TiN, [ 145,146 ] B, [ 147–149 ] and others, [ 150–152 ] have been confirmed to improve both the mechanical and thermoelectric performance of TE materials.…”