Development of Nanostructured Bi<sub>2</sub>Te<sub>3</sub> with High Thermoelectric Performance by Scalable Synthesis and Microstructure Manipulations
Chhatrasal Gayner, Luke T. Menezes, Yuriy Natanzon, Yaron Kauffmann, Holger Kleinke, Yaron Amouyal
Abstract
Nanostructuring of thermoelectric (TE) materials leads to improved energy conversion performance; however, it requires a perfect fit between the nanoprecipitates’ chemistry and crystal structure and those of the matrix. We synthesize bulk Bi 2 Te 3 from molecular precursors and characterize their structure and chemistry using electron microscopy and analyze their TE transport properties in the range of 300–500 K. We find that synthesis from Bi 2 O 3 + Na 2 TeO 3 precursors results in n-type Bi 2 Te 3 containing a high number density ( N v ∼ 2.45 × 10 23 m –3 ) of Te-nanoprecipitates decorating the Bi 2 Te 3 grain boundaries (GBs), which yield enhanced TE performance with a power factor (PF) of ∼19 μW cm –1 K –2 at 300 K. First-principles calculations validate the role of Te/Bi 2 Te 3 interfaces in increasing the charge carrier concentration, density of states, and electrical conductivity. These optimized TE coefficients yield a promising TE figure of merit ( zT ) peak value of 1.30 at 450 K and an average zT of 1.14 from 300 to 500 K. This is one of the cutting-edge zT values recorded for n-type Bi 2 Te 3 produced by chemical routes. We believe that this chemical synthesis strategy will be beneficial for future development of scalable n-type Bi 2 Te 3 based devices.