# AlxCoCrFeNi High-Entropy Alloys Enable Simultaneous Electrical and Mechanical Robustness at Thermoelectric Interfaces

## TL;DR

This paper introduces a new high-entropy alloy that improves the electrical and mechanical performance of thermoelectric generators at high temperatures.

## Contribution

AlxCoCrFeNi high-entropy alloys are proposed as a novel interfacial material for thermoelectric generators with simultaneous electrical and mechanical robustness.

## Key findings

- The HEA/p-SKD interface formed a stable, defect-free (Fe,Ni,Co,Cr)Sb phase with low interfacial resistivity.
- The interface retained high shear strength after 16 days of aging at 773 K and 100 thermal cycles.
- The alloy shows exceptional thermo-mechanical stability, making it ideal for thermoelectric applications.

## Abstract

The interface between high-performance thermoelectric materials and electrodes critically governs the conversion efficiency and long-term reliability of thermoelectric generators under high-temperature operation. Here, we propose AlxCoCrFeNi high-entropy alloys (HEA) as barrier layers to bond Cu-W electrodes with p-type skutterudite (p-SKD) thermoelectric materials. The HEA/p-SKD interface exhibited excellent chemical bonding with a stable and controllable reaction layer, forming a dense, defect-free (Fe,Ni,Co,Cr)Sb phase (thickness of ~2.5 μm) at the skutterudites side. The interfacial resistivity achieved a low value of 0.26 μΩ·cm2 and remained at 7.15 μΩ·cm2 after aging at 773 K for 16 days. Moreover, the interface demonstrated remarkable mechanical stability, with an initial shear strength of 88 MPa. After long-term aging for 16 days at 773 K, the shear strength retained 74 MPa (only 16% degradation), ranking among the highest reported for thermoelectric materials/metal joints. Remarkably, the joint maintained a shear strength of 29 MPa even after 100 continuous thermal cycles (623–773 K), highlighting its outstanding thermo-mechanical stability. These results validate the AlxCoCrFeNi high-entropy alloys as an ideal interfacial material for thermoelectric generators, enabling simultaneous optimization of electrical and mechanical performance in harsh environments.