Enhanced thermal reliability of p-type PbTe thermoelectric devices through interfacial design with an FeCoNiCr multicomponent diffusion barrier

Abstract

The long-term reliability of thermoelectric devices critically depends on the thermal and chemical stability of their diffusion barriers. Conventional single-metal barriers often fail to simultaneously satisfy the requirements of stability, electrical compatibility, and mechanical integrity. To address these limitations, we introduce a quaternary FeCoNiCr alloy as a diffusion barrier for p-type PbTe. The alloy exhibits an enhanced coefficient of thermal expansion (16.2 × 10⁻⁶ K⁻¹) compared with pure Fe (15 × 10⁻⁶ K⁻¹), yielding improved thermal compatibility with PbTe. Samples sintered at 923 K achieved a low interfacial resistivity of 3.1 µΩ cm². Owing to the in situ formation of a thermodynamically stable Cr₃Te₄ phase, the FeCoNiCr/PbTe interface retained structural integrity and a low resistivity of 3.0 µΩ cm² even after 500 h of aging at 723 K. At a 500 K temperature difference, the thermoelectric leg delivered a maximum output power of 0.22 W and a peak conversion efficiency of 7.8%, with negligible degradation after aging, demonstrating the excellent interfacial and thermal stability of the multicomponent alloy.