Next Generation Additive Manufacturing: Laser Sintering and Melting of Thermoelectric Materials

Thermoelectric generators offer the potential for effective waste heat recovery in combustion applications e.g. engines. However, traditional manufacturing of TEGs involves assembly and integration processes which lead to performance degradation and high costs. Additive manufacturing methods of semiconductor energy conversion materials could lead to higher efficiency, cost-effective energy technologies. This project investigated additive laser sintering and melting of thermoelectric materials. The results advance semiconductor materials processing knowledge to enable flexible manufacturing and device design of thermoelectric generators. The project resulted in the first-ever demonstration of selective laser melting on thermoelectric half-Heusler material. Challenges associated with thermoelectric material powder morphology were overcome to enable spreading of thin 100 m thick layers. Multiple samples were produced in a layer-by-layer additive manufacturing approach. Changes in material phase occurred during laser processing. While the original half-Heusler phase could be regained through a post-processing annealing step, the phase change may indicate a critical challenge with selective laser melting of half-Heusler materials. Future work necessitates a comparison of phase changes in half-Heusler materials to other thermoelectric material in order to determine which materials may be most compatible with the selective laser melting process.