Boosting thermoelectric performance of n-type Bi2Te2.7Se0.3 alloy by 3D printing induced in-situ texture engineering

Abstract

Rational design of microstructure in thermoelectric materials is conducive to improve the thermoelectric properties. Bismuth telluride alloys are easy to form texture during sintering due to the weak van der Waals bonding between the Te-Te layers. However, high content of texture will greatly deteriorate the out-of-plane electrical properties and in-plane thermal properties. Herein, the bulk sample of n-type Bi2Te2.7Se0.3 with controllable texture degree was obtained by selective laser melting (SLM) 3D printing technology. By setting the appropriate laser power density, the epitaxial growth of some grains in the melt pool can be suppressed and controlled texturing of the material can be achieved. The printed Bi2Te2.7Se0.3 alloy shows texture-dependent thermoelectric properties by texture control ensuring that the Bi2Te2.7Se0.3 alloy has both high carrier mobility and strong phonon scattering, leading to a competitive ZT ∼ 1.21 at 373 K. Based on excellent thermoelectric properties, we have assembled a 127-pair thermoelectric module with a conversion efficiency of 6.2 % at a temperature difference of 213 K, and the corresponding output performance is comparable to that of state-of-art bismuth telluride thermoelectric modules. This study illustrates the potential of texture engineering based on SLM printing in developing high-performance thermoelectric materials.