Enhanced Interfacial Reliability and Mechanical Strength of CoSb₃-Based Thermoelectric Joints with Rationally Designed Diffusion Barrier Materials of Ti-Based Alloys

Abstract

To achieve high-performance thermoelectric (TE) devices, constructing a good interfacial connection between TE materials and electrodes is as important as having high figure-of-merit TE materials. Although CoSb 3 -based TE devices have received great attention for power generation recently, the limited long-term service stability is the main obstruct for their applications. In this work, we have prepared two kinds of Ti-based alloys (Ti 83.7 Al 10.7 Si 5.6 and Ti 74 Ni 26 ) as the diffusion barrier layer of CoSb 3 -based TE joints by the spark plasma sintering method and have systematically investigated their interfacial behaviors during the aging process. The performances of contact resistivity and mechanical strength for Ti 74 Ni 26 /Yb 0.4 Co 3.8 Fe 0.2 Sb 12 TE joints are good before aging treatment but gradually deteriorate during the aging process, which should be ascribed to the phase-transition-induced negative thermal expansion in Ti−Ni alloys. On the other hand, Ti 83.7 Al 10.7 Si 5.6 /Yb 0.4 Co 3.8 Fe 0.2 Sb 12 TE joints show both low contact resistivity (<10 μΩ•cm 2 ) and high mechanical strength (>20 MPa) before and after 16-day aging at 500 °C, which is originated from the matching of the coefficient of thermal expansion (CTE) and the formation of network structures in Ti−Al−Si alloys. We have also prepared an eight-couple TE module of p-Ge 0.9 Sb 0.1 TeB 0.01 /n-Yb 0.4 Co 3.8 Fe 0.2 Sb 12 and have measured its corresponding device performance. Our work has demonstrated that the matched CTE and network structures in the Ti−Al−Si alloy are key to obtain high-performance CoSb 3 -based TE joints for long-term service.

Highly tailored gap-like structure for excellent thermoelectric performance

“…Other than this, neither the electrical properties nor the thermal properties deteriorated more than 10% (near the instrument uncertainty) over the entire temperature range after the cycle tests, suggesting exceptional stability. Comparing our transport properties data with the selected reported materials [50][51][52][53] for mediumtemperature single-stage TE modules, the high temperature k lat value of Sb 2 Te 3 (Ge 0.995 Yb 0.005 Te) 17 was competitive and the PF, ZT max , and ZT ave from our results presented significant superiority, boosting the application potential of Sb 2 Te 3 (GeTe) nbased TE modules.…”

“…4 and 54 that deviated from these ranges were not considered in this study. According to the power density algorithm from these studies, 50–54 our module contained an outstanding power density value of 1.25 W cm −2 , which was 20% higher than the former record value for a GeTe-based module. 50,51 Furthermore, to ensure the repeatability of our Sb 2 Te 3 (Ge 0.995 Yb 0.005 Te) 17 -based module, another piece was fabricated, and the detailed performance is shown in Fig.…”

“…The linear relationships over different hot-side temperatures suggested the good reliability of the joint. The completely low internal resistance (from 0.09 to 0.12 Ω) during the test, compared to the other GeTe-based modules, 50,51,54 implied the promising potentials of the Sb 2 Te 3 (GeTe) n -based TE modules.…”

“…To further consolidate the material superiority caused by gap-like structural tailoring, and to validate the major effects on module-level performance, a 20 Â 20 mm S12 (ESI †), revealed that a good interfacial connection was prepared with a homogeneous Ni layer of 14 mm, and the resistance was 11.44 mO cm 2 , which was much lower than that of the reported sintered barrier interfaces. 50,51 Thus, as shown in Fig. 5(a), the I-V curve, which reflected the internal resistance of TE module dynamically and directly, was measured by a commercial instrument, PEM-2.…”

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

“…[ 16,25 ] This problem can be alleviated by introducing appropriate diffusion barriers between electrodes and TE legs. [ 25–29 ]…”