Selective Laser Melting of Half-Heusler Thermoelectric Materials

Traditional thermoelectric device manufacturing uses machining, assembly, and integration steps which lead to material waste and performance limitations. The approach offers little flexibility in designing thermoelectric module geometry. Additive manufacturing can overcome these challenges, but it has not been demonstrated for inorganic thermoelectric materials, particularly those geared toward mid-/high-temperature applications. This work describes selective laser melting, an additive manufacturing process which locally melts successive layers of material powder to construct three-dimensional objects. The work shows the first-ever demonstrations of selective laser melting applied to half-Heusler thermoelectric materials: ZrNiSn, and Hf0.3Zr0.7CoSn0.3Sb0.7/nano-ZrO2. Laser processing parameters critically affects the formation and appearance of ingots, and we found laser energy density is useful but cannot be the single consideration for the SLM process. The fabricated ingots are generally porous with rough surfaces. They are characterized through powder XRD and TGA. The results consistently show that produced parts preserved most of the original chemical structures with small chemical changes due to decomposition and oxidation during the selective laser melting process. The work demonstrates selective laser melting is feasible for half-Heusler thermoelectric materials.