Scalable colloidal synthesis of Bi 2 Te 2.7 Se 0.3 plate-like particles give access to a high-performing n-type thermoelectric material for low temperature application

Colloidal synthesis is harnessed for the gram-scale preparation of hexagonal-shaped plate-like Bi Te Se particles, yielding nearly 5 g of the product in one experiment. The resultant textured particles are highly crystalline, phase-pure, chemically uniform, and can serve as a starting material for the preparation of bulk thermoelectrics for room temperature applications. The consolidation occurs spark plasma sintering, which affords nanostructured n-type Bi Te Se material exhibiting a high figure of merit ≈ 1 at 373 K with an average ≈ 0.93 (300-473 K). Our experimental and theoretical studies indicate that the high thermoelectric performance is attributed to a favorable combination of the resultant transport properties. Specifically, bottom-up formation of the plate-like particles results in the substantial reduction of thermal conductivity by nanostructuring as observed experimentally and can be ascribed to phonon scattering at grain boundaries and suppressed bipolar conduction. When coupled with high electrical conductivity, which is preserved at the bulk scale as confirmed by calculations, these factors boost the thermoelectric performance of the as-synthesized n-type Bi Te Se bulk nanostructured alloy to the state-of-the-art level. The combination of a newly developed scalable colloidal synthesis with optimized spark plasma sintering constitutes a convenient route to nanostructured bulk thermoelectrics, which is an interesting pathway for the preparation of simple and complex thermoelectric chalcogenides.