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 high-temperature 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 mm² PbTe module exhibits a conversion efficiency of 11.6% at 803 K and shows no detectable degradation within the experimental uncertainty over 200 thermal cycles. These findings establish interfacial stress management as a critical design principle for achieving durable high-temperature thermoelectric modules.