Bi2Te3 filaments via extrusion and pressureless sintering of Bi2Te3-based inks

Inks containing sub-20 µm particles of doped bismuth telluride (n-type Bi₂Te_2.73Se_0.3 or p-type (Bi_0.5Sb_1.5)Te₃) are extruded into 330 µm diameter filaments. When solid-state sintered up to 857 K under no pressure, the filaments only partially densify, with over 20% porosity remaining. Coating the filament with TeO₂ powder, followed by hydrogen reduction to liquid Te, enables liquid phase sintering at 710 K, with rapid densification to less than 5% porosity within 1 h. Coating with a stoichiometric blend of Bi₂O₃ + 3TeO₂ powders, followed by hydrogen reduction to liquid Bi and Te, provides transient liquid phase sintering at 808 K and subsequent reaction to Bi₂Te₃, resulting in fast filament densification, to less than 5% porosity within 10 min without residual Te.