Investigation of nanopowder laser sintering for additive manufacturing of thermoelectric devices

Abstract

A beam of green light (532nm wavelength) produced by a 500mW diode-pumped solid-state laser was focused onto bismuth telluride nanopowder on glass substrates. Powder layers were deposited via spray-coating of colloidal dispersions of bismuth telluride in ethanol and methanol. Scans were made with 250, 325, and 400mW beam power at scan velocities of 0.02, 0.08, 0.14, and 0.20mm/s. Consolidated samples were analyzed with optical microscopy and surface profilometry. Trends in the data indicate an inverse relationship between line widths and scan velocity, a proportional relationship between line thicknesses and scan velocity, and an increase in surface roughness with increasing velocity. Beam power relationships are less definitive, but increasing beam power leads to increased line width, as well as decreased thickness and roughness, indicative of increased densification. The experimental process highlighted above produces better repeatability than earlier attempts and considerations for future improvements are discussed.