Broad Temperature Plateau for High Thermoelectric Properties of n-Type Bi₂Te_2.7Se_0.3 by 3D Printing-Driven Defect Engineering

Abstract

High-energy-conversion Bi 2 Te 3 -based thermoelectric generators (TEGs) are needed to ensure that the assembled material has a high value of average figure of merit (ZT ave ). However, the inferior ZT ave of the n-type leg severely restricts the large-scale applications of Bi 2 Te 3 -based TEGs. In this study, we achieved and reported a high peak ZT (1.33) of three-dimensional (3D)printing n-type Bi 2 Te 2.7 Se 0.3 . In addition, a superior ZT ave of 1.23 at a temperature ranging from 300 to 500 K was achieved. The high value of ZT ave was obtained by synergistically optimizing the electronic-and phonon-transport properties using the 3D-printing-driven defect engineering. The nonequilibrium solidification mechanism facilitated the multiscale defects formed during the 3D-printed process. Among the defects formed, the nanotwins triggered the energy-filtering effect, thus enhancing the Seebeck coefficient at a temperature range of 300−500 K. The effective scattering of wide-frequency phonons by multiscale defects reduced the lattice thermal conductivity close to the theoretical minimum of ∼0.35 W m −1 k −1 . Given the advantages of 3D printing in freeform device shapes, we assembled and measured bionic honeycombshaped single-leg TEGs, exhibiting a record-high energy conversion efficiency (10.2%). This work demonstrates the great potential of defect engineering driven by selective laser melting 3D-printing technology for the rational design of advanced n-type Bi 2 Te 2.7 Se 0.3 thermoelectric material.

Enhancement in thermoelectric performance of hydrothermally synthesized Ca and Sb co-doped Bi2Te3 nanostructures

“…Also, from FESEM images, it can be observed that large grains are formed in nanostructured samples. So, due to energy filtering effect, these large grains reduced the Seebeck coefficient of the samples [48][49][50][51][52]. The value of Seebeck coefficient is close to the reported values in the literature [35].…”