Revealing electrical and mechanical degradation of Ni/Bi₂Te₃ interface through the quantitative interfacial diffusion analysis

Bismuth telluride (Bi₂Te₃)-based thermoelectric devices exhibit significant potential for energy harvesting and thermal management. However, device reliability and further development are critically limited by interface-induced failures, largely because quantitative failure analysis methods are lacking. This study systematically investigates interfacial degradation mechanisms and establishes a method for device lifetime prediction. First, accelerated thermal stress experiments are designed to analyze the Ni diffusion behavior at interface of different-type Bi₂Te₃-based TE materials, thereby determining the quantitative relationship among temperature (T), duration (t), activation energy (ΔE) and diffusion coefficient (D). Besides, the Ni diffusion depth (x) is confirmed to scale linearly with the square root of time (x∝t^1/2) for a given diffusion coefficient, which is consistent with Fick's second law (D=x²/4t). Moreover, both interfacial specific contact resistivity (ρ_c) and tensile strength (σ_s) exhibit linear correlations with Ni diffusion depth under a specific degradation mechanism, enabling quantitative assessment of interface stability. Ultimately, adopting standard resistance failure criteria, we completely propose a method for quantitative lifetime prediction, which might provide universal applicability for the reliability assessment of thermoelectric devices and advance the prediction method of interface-induced failure analysis.