Rational Design of Bi<sub>2</sub>Te<sub>3</sub> Polycrystalline Whiskers for Thermoelectric Applications

Bi<sub>2</sub>Te<sub>3</sub> polycrystalline whiskers consisting of interconnected nanoplates have been synthesized through chemical transformation from In<sub>2</sub>Te<sub>3</sub> polycrystalline whisker templates assembled by nanoparticles. The synthesized Bi<sub>2</sub>Te<sub>3</sub> whiskers preserve the original one-dimensional morphology of the In<sub>2</sub>Te<sub>3</sub>, while the In<sub>2</sub>Te<sub>3</sub> nanoparticles can be transformed into the Bi<sub>2</sub>Te<sub>3</sub> thin nanoplates, accompanied by the formation of high-density interfaces between nanoplates. The hot-pressed nanostructures consolidated from Bi<sub>2</sub>Te<sub>3</sub> polycrystalline whiskers at 400 °C demonstrate a promising figure of merit (<i>ZT</i>) of 0.71 at 400 K, which can be attributed to their low thermal conductivity and relatively high electrical conductivity. The small nanoparticles inherited from the polycrystalline whiskers and high-density nanoparticle interfaces in the hot-pressed nanostructures contribute to the significant reduction of thermal conductivity. This study provides a rational chemical transformation approach to design and synthesize polycrystalline microstructures for enhanced thermoelectric performances.