Interfacial Stress Limits PbTe Module Reliability: Porous Fe Foam Mitigates Thermal-Mismatch Stress

Abstract

Long-term reliability of PbTe-based thermoelectric modules is constrained by a failure mechanism that conventional diffusion-barrier approaches do not address: interfacial thermal-mechanical stress, rather than chemical interdiffusion alone. Here we show that cyclic stress accumulation is the dominant driver of performance degradation under hightemperature thermal cycling. To mitigate this failure pathway, we introduce a mechanically adaptive porous Fe foam as a stress-relief interlayer. The deformable open-cell structure dissipates interfacial strain while permitting metallurgical infiltration that preserves ohmic contact and low resistance. By optimizing porosity, a stable interface architecture is achieved that maintains high electrical performance. A 20 × 20 mm 2 PbTe module exhibits a conversion efficiency of 11.6% at 803 K and shows no measurable degradation over 200 thermal cycles. These findings establish interfacial stress management as a critical and previously underappreciated design principle for achieving durable high-temperature thermoelectric modules..