Direct Ink Writing (3D Printing) of Robust, Highly Efficient, Double‐Half‐Heusler Thermoelectric High‐Entropy Alloy

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Abstract
In thermoelectric (TE) devices, geometry of the TE‐leg has a significant impact on its energy conversion efficiency. TE leg fabrication still relies on traditional methods with regular solid shapes which limits the conversion efficiency. In the present work, different geometries (solid, mesh, hollow, and honeycomb) based on a double‐half‐Heusler (hH) (Ti 1.75 Zr 0.25 Ni 1.5 Fe 0.5 SnSb) high‐entropy alloy are 3D printed using direct ink writing technique. Through the rheological properties, good shear‐thinning characteristics and excellent printability are shown. X‐ray diffraction of the as‐cast and sintered 3D‐printed structures confirms the formation of dominant hH phase. Using infrared imaging, it is revealed that the heat distribution in these structures decreases as an order of as‐cast, solid, mesh, hollow, and honeycomb geometries due to improved surface area to volume ratio respectively. Using X‐ray micro‐computed tomography, the total porosity of the 3D‐printed sample is shown to be around 24.89%. Honeycomb‐shaped structure shows highest temperature gradient (from top to bottom region of sample) of 174 °C as compared to as cast (60.1 °C), which is further validated using finite‐element analysis. In addition, specific energy absorption of 3D‐printed structure is enhanced by 18.5% compared to that of as‐cast structure.

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