Texturization and Dense Dislocations Boost Elastic Bendability of Metallic Thermoelectric Generator

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 100 000 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.