Elastic strain constitutes a decisive factor in determining the recoverable deformability of thermoelectric materials. Plastic deformation for microstructure engineering has been demonstrated as a viable approach to enhance the elastic strain. However, this approach is highly dependent on the material’s plasticity, which is rather limited by the rigidity for the majority of inorganic semiconducting thermoelectric materials. Thermocouple materials, as metallic thermoelectric materials, possess a favorable plasticity, motivating this work to focus on the elastic bendability of a metallic thermoelectric generator that is composed of K-type thermocouple components, namely p-type Ni₉₀Cr₁₀ and n-type Ni₉₅Al₂Mn₂Si. The cold-rolling process enables a large elastic modulus and a high yield strength, thanks to the texturized direction along <111>, and dense dislocations and refined grains, respectively, eventually resulting in a 400% increase in the elastic strain. Such superior elasticity ensures the preservation of the initial transport properties for the rolled films even after being bent 100000 times within a radius of ~8 mm. A power output of ~414 μW is achieved in a ten-leg flexible thermoelectric device, suggesting its substantial potential for powering wearable electronics.

Thermal stability of thermoelectric devices plays a pivotal role in their practical applications. Chemical reaction/diffusion between thermoelectric materials and electrodes is one of the primary factors contributing to the degradation/failure of device performance at elevated temperatures. Introducing barrier layers to impede the behavior of chemical reactions has emerged as an effective approach for averting the failure of these devices. In this work, the FeSi is revealed to be a potent material of barrier layer in high-performance Mg₂Si_0.3Sn_0.7 thermoelectric material based on the considerations of interfacial reaction energy and sinterability. The well-established bond in Mg₂Si_0.3Sn_0.7/FeSi joint results in a low contact resistivity of ~20 μΩ⸱cm² and a conversion efficient of ~6.5% for the Mg₂Si_0.3Sn_0.7 single-leg device is achieved at a temperature difference of ~290 K. Long-term measurements of the device at a hot-side temperature of 600 K reveal that the performance remains nearly invariable as time further increases, which suggests that the FeSi layer retards the chemical reaction/diffusion.