Warm Metalworking for Brittle Liquid‐Nitrogen‐Temperature Thermoelectric Materials

Abstract Thermoelectric cooling around liquid nitrogen temperature is vital to electronics and optoelectronics. This application calls for both high thermoelectric performance and superior mechanical properties to ensure decent deformability and processibility, which is nonetheless largely overlooked. In this work, the excellent temperature‐induced plasticity of Bi 0.85 Sb 0.15 as the classic liquid‐nitrogen‐temperature thermoelectric material is reported. The material shows large compressive strains exceeding 60% above ≈423 K, as well as a decent compressive strain of ≈21.5% at room temperature. By microstructural and atomistic analyses, the plasticity at slightly elevated temperature is ascribed mainly to the grain elongation and reorientation, which is rooted in the thermally amplified atomic vibration and thus reduced slip barrier energy. The low brittle‐to‐ductile transition temperature allows the material to be warm‐processed into desired shapes in a metal‐like manner with high efficiency and low losses. Particularly, the warm‐extruded Bi 0.85 Sb 0.15 shows comparably high thermoelectric performance as well as larger strength and compressibility as compared to the original bulks. These findings enable warm metalworking to promote the development of miniaturized and hetero‐shaped thermoelectric cooling techniques around liquid nitrogen temperature.