Preparing bulk Cu-Ni-Mn based thermoelectric alloys and synergistically improving their thermoelectric and mechanical properties using nanotwins and nanoprecipitates

Cu-Ni-Mn based alloys have long been considered as potential thermoelectric materials because of their Seebeck effect and large power factor. In this study, bulk Cu-Ni-Mn based alloys with nanostructures were prepared via melting and cryorolling, and their thermoelectric and mechanical properties were analyzed. A large number of nanotwins and nanoprecipitates were observed in the prepared alloys using transmission electron microscopy. These observations indicate that the bulk Cu-Ni-Mn alloys with nanostructures can be successfully prepared using conventional melting-solidification-rolling technology. The Cu-Ni-Mn alloy containing nanotwins exhibits a promising Seebeck coefficient of ∼ −72.8 μVK⁻¹ and power factor of ∼11000 μWm⁻¹K⁻² at 1073 K, and thereby, a high output power density. The bulk Zr-doped Cu-Ni-Mn alloy containing nanoprecipitates and nanotwins exhibits a lower thermal conductivity of ∼32.9 Wm⁻¹K⁻¹ and a 37.5% higher ZT of ∼0.22 at 773 K. Enhanced mechanical properties make the Cu-Ni-Mn based alloys a promising candidate for thermoelectric application. Our discovery provides a promising strategy to improve the thermoelectric and mechanical properties of materials with high thermal conductivity through the introduction of nanotwins and nanoprecipitates.