Meso-, micro- And nano-structures induced in bismuth telluride thermoelectric materials by laser additive manufacturing

Thermoelectric devices are solid-state energy conversion devices that are used in thermal management and waste heat recovery applications. Current thermoelectric devices are limited in their geometries, and the manufacturing process is labor-intensive. The traditional manufacturing methods limit the widespread use of thermoelectric modules in potential application areas. To address this issue and expand the use of thermoelectric devices, we investigated laser powder bed fusion, an additive manufacturing technique that is also known as selective laser melting. We performed selective laser melting on bismuth telluride, a common thermoelectric material. This work explored Bi₂Se₀₃Te₂₇, an n-type thermoelectric material. After laser processing, the meso-, micro-, and nanostructure of selectively laser melted samples were analyzed to identify the relationship between the laser parameters and processed materials. The meso- and micro-structure was investigated with optical and scanning electron microscopy to identify the grain structure and morphology. The nanostructure was analyzed using transmission electron microscopy to explore the location and density of dislocations and point defects. The results reveal the impact of selective laser melting process parameters on n-type bismuth telluride and guide future work in determining the process-structure relationship for laser additive manufacturing of thermoelectric devices.