Enhanced thermoelectric performance of solution-derived bismuth telluride based nanocomposites via liquid-phase Sintering

Highlights: • Liquid-phase sintering strategy is introduced to the synthesis of nanostructured bulk thermoelectric materials. • Lattice and bipolar thermal conductivity are both greatly reduced in these solution-derived samples • The average ZT values reach up to 1.59±0.16 for p-type Bi_0.5Sb_1.5Te₃ and 0.98±0.07 for n-type Bi₂Te_2.7Se_0.3 at 370 K. Bismuth telluride based thermoelectric materials show great promise in electricity generation from waste heat and solid-state refrigeration, but improving their conversion efficiency with economical approaches for widespread use remains a challenge. An economical facile bottom-up approach has been developed to obtain nanostructured powders, which are used to build bulk thermoelectric materials. Using excess tellurium as sacrificial additive to enable liquid-phase sintering in the spark plasma sintering process, the lattice and bipolar contributions to the thermal conductivity are both greatly reduced without compromising too much the power factor, which leads to the achievement of high figure of merit (ZT) in both n-type and p-type bismuth telluride based nanocomposites. The ZT values are 1.59±0.16 for p-type Bi_0.5Sb_1.5Te₃ and 0.98±0.07 for n-type Bi₂Te_2.7Se_0.3 at 370 K, which are significantly high for bottom-up approaches. These results demonstrate that solution-chemistry approaches as facile, scalable and low-energy-intensive ways to achieve nanopowders, combined with liquid-phase sintering process, can open up great possibilities in developing high-performance low-price thermoelectric bulk nanocomposites.