Achieving superior performance in thermoelectric Bi0.4Sb1.6Te3.72 by enhancing texture and inducing high-density line defects

Abstract

Miniaturization of efficient thermoelectric (TE) devices has long been hindered by the weak mechanical strength and insufficient heat-to-electricity conversion efficiency of zone-melted (ZM) ingots. Here, we successfully prepared a robust high-performance p-type Bi 0.4 Sb 1.6 Te 3.72 bulk alloy by combining an ultrafast thermal explosion reaction with the spark plasma sintering (TER-SPS) process. It is observed that the introduced excess Te not only enhances the (00l)-oriented texture to ensure an outstanding power factor (PF) of 5 mW m −1 K −2 , but also induces extremely high-density line defects of up to 10 11 -10 12 cm −2. Benefiting from such heavily dense line defects, the enhancement of the electronic thermal conductance from the increased electron mobility is fully compensated by the stronger phonon scattering, leading to an evident net reduction in total thermal conductivity. As a result, a superior ZT value of~1.4 at 350 K is achieved, which is 40% higher than that of commercial ZM ingots. Moreover, owing to the strengthening of grain refinement and highdensity line defects, the mechanical compressive stress reaches up to 94 MPa, which is 154% more than that of commercial single crystals. This research presents an effective strategy for the collaborative optimization of the texture, TE performance, and mechanical strength of Bi 2 Te 3 -based materials. As such, the present study contributes significantly to the future commercial development of miniature TE devices.

High ZT in p-type thermoelectric (Bi,Sb)2Te3 with built-in nanopores

“…[22][23][24][25] Further microstructure engineering can also improve the electrical transport properties in many ways. For example, proper grain size enlargement 8,26,27 and texturing 7,[28][29][30] can increase the chargecarrier mobility, and nano-inclusions with an appropriate band structure increase the Seebeck coefficient via the energy filtering effect. [31][32][33][34] Therefore, the power factor (PF, which is equal to sS 2 ) of powder-processed Bi 2 Te 3 -based materials has been improved to 4.0-5.0 mW m À1 K À2 , which equals those obtained using zonemelting or the Bridgman technique.…”

(Bi,Sb)2Te3/SiC nanocomposites with enhanced thermoelectric performance: Effect of SiC nanoparticle size and compositional modulation

“…Achieving high ZT values is challenging because of the strong coupling of S, σ, and κ tot (mainly κ e ). Nevertheless, great progress has been made in improving the ZT values using a variety of methods such as nanostructure engineering [8][9][10], electronic band engineering [11][12][13], energy-filtering effect [14][15][16][17], defects engineering [18][19][20][21], as well as seeking or exploring materials with intrinsically low thermal conductivity [22][23][24][25][26].…”

Enhancing the Thermoelectric and Mechanical Properties of Bi0.5Sb1.5Te3 Modulated by the Texture and Dense Dislocation Networks

“…Therefore, in order to maintain a high F , a moderate P should be adopted. We found the sample processed by under 20 MPa exhibited a high F of 0.8, which was much higher than that of the polycrystalline materials prepared by the traditional PM method. − ,,− XRD pole figures in Figure c,d further confirm that the sample of P = 20 MPa shows the strong (00 l )-oriented texture [since there are almost no other texture signs of the (015) and (110) planes]. From the SEM images of the samples processed under various pressures (Figure S4), it can be found that the lower the applied pressure, the smaller the misplaced laminated structure of the cleavage sheets and thus the higher the textured degree.…”

“…Theoretically, the in-plane carrier mobility (μ) is about 3 times as high as that of out-of-plane, while the in-plane lattice thermal conductivity (κ L ) is about 2-fold higher than that of out-of-plane . This leads to strong anisotropic TE performance, where the in-plane ZT value is remarkably better than that of the out-of-plane. , Nevertheless, in order to achieve these sharp anisotropic TE properties in polycrystalline samples, it is a prerequisite to prepare materials with a strongly textured microstructure. − High textures are usually of great benefit to the transport of electrons and thus lead to an obvious increase of l e and μ. In the meantime, l ph should be diminished to obtain a lower κ L so as to mitigate the adverse contribution of electronic thermal conductivity (κ e ∝ μ) to κ t . − …”