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

Abstract

High‐performance thermoelectric (TE) devices require not only a high figure of merit (ZT) but also mechanical strength and thermal stability. Here, a simultaneous enhancement of ZT as well as mechanical properties is obtained in GeTe‐based alloys by adding boron. This material is then assembled with n‐type CoSb3 skutterudite into TE modules. The improved ZT values result from the increase in charge carrier mobility due to the reduced interfacial barrier height. A peak ZT of 2.2 at 773 K can be achieved in Ge0.84Pb0.1Sb0.06TeB0.07, which shows a negligible change in the coefficient of thermal expansion upon the phase transition from the rhombohedral to the cubic phase, ensuring good thermal stability of the device. Resulting from the boron‐induced grain refinement and dispersion strengthening, the average compressive strength and Vickers hardness of Ge0.9Sb0.1TeB0.07 can be enhanced to ≈227 MPa and ≈202 Hv, respectively. The improved mechanical properties facilitate the assembly of devices and lower the interfacial contact resistance. As a synergy of increased ZT and mechanical strength, a high output power density of ≈1.76 W cm−2 at ΔT = 425 K and an energy conversion efficiency of 7.4% at ΔT = 477 K can be achieved in the TE modules.

High‐Performance Thermoelectric Material and Module Driven by Medium‐Entropy Engineering in SnTe

“…This is also a competitive value among the reported common TE candidates, and even higher than GeTe with recognized high H V of ≈110. [60][61][62][63] The superior mechanical strength indeed provides great convenience for the TE module machining and assembling process. As presented in Figure 7e and Figure S3 of Supporting Information, the p-type legs composed of our SnTe-based MEAs maintain good integrity.…”

“…[64,66,67] Additionally, the obtained η max of 6.3% with a ΔT of 350 °C is also competitive compared with previously reported excellent GeTe-, PbTe-, and half-Heusler-based mid-temperature TE modules. [63,[68][69][70] Furthermore, to verify the theoretical maximum η of the module, we also conduct the multi-physics field simulation (see Figure S5 in Supporting Information). The predicted η max (Figure 7f dotted red line) is 7.4% at ΔT = 350 °C, and it is ≈18% higher than the measured value.…”

High figure-of-merit and power generation in high-entropy GeTe-based thermoelectrics

“…1B), respectively. These experimental values were among the highest in the entire TE community (4,(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45), indicating an important step toward TE applications.…”

Improved zT in Nb5Ge3–GeTe thermoelectric nanocomposite

“…Bi or Sb). 20,[41][42][43][44][45][46][47][48][49][50][51] In addition, doping or alloying with Ti, Cr, Bi 2 Te 3 , PbTe, Cu 2 Te, AgBiSe 2 , and heat treatment have also been explored. 41,[52][53][54][55][56][57][58][59][60][61][62][63] In addition, extremely rapid cooling using liquid nitrogen have also been reported to enhance GeTe performance.…”

“…Unfortunately, the phase transition usually results in poor mechanical properties. [75][76][77] In addition, the lattice thermal conductivity is generally higher in cubic phase, therefore limiting the maximum performance of cubic GeTe.…”