Experimental Studies on Anisotropic Thermoelectric Properties and Structures of n-Type Bi₂Te_2.7Se_0.3

Abstract

The peak dimensionless thermoelectric figure-of-merit (ZT) of Bi(2)Te(3)-based n-type single crystals is about 0.85 in the ab plane at room temperature, which has not been improved over the last 50 years due to the high thermal conductivity of 1.65 W m(-1) K(-1) even though the power factor is 47 x 10(-4) W m(-1) K(-2). In samples with random grain orientations, we found that the thermal conductivity can be decreased by making grain size smaller through ball milling and hot pressing, but the power factor decreased with a similar percentage, resulting in no gain in ZT. Reorienting the ab planes of the small crystals by repressing the as-pressed samples enhanced the peak ZT from 0.85 to 1.04 at about 125 degrees C, a 22% improvement, mainly due to the more increase on power factor than on thermal conductivity. Further improvement is expected when the ab plane of most of the small crystals is reoriented to the direction perpendicular to the press direction and grains are made even smaller.

Studies on the Bi2Te3–Bi2Se3–Bi2S3system for mid-temperature thermoelectric energy conversion

“…6(d) It was reported that re-orientation of randomly distributed grains help to achieve a ZT enhancement of n-type Bi 2 Te 3 -based thermoelectric materials. 9,11 Here, a twice-repressing process was used to get stronger (00l)-texture, in contrast to the previous oncerepressing process, and finally higher ZT along the direction perpendicular to the press direction. Fig.…”

Enhanced thermoelectric performance in spark plasma textured bulk n-type BiTe2.7Se0.3 and p-type Bi0.5Sb1.5Te3

“…After repressing, nanosized powders of n-type bismuth telluride showed 22% ZT enhancement. 18 Here, we present a comparative study on bulk p and n-type bismuth telluride using SPS and Spark plasma texturing (SPT), a two step process using SPS and its consequences on the microstructure, texture and thermoelectric performance.…”

Surfactant-Free Synthesis of Bi2Te3−Te Micro−Nano Heterostructure with Enhanced Thermoelectric Figure of Merit

“…Z. Ren and co-workers have done a very detailed study on the anisotropic TE properties of Bi 2 Te 2.7 Se 0.3 . 1 In-plane conductivity (perpendicular to press direction) is reported to be higher for both electrical and thermal test than cross-plane (parallel to press direction) by about 10%-20%. Therefore, in this work, we applied a modified factor ~0.8 to estimate the cross-plane electrical conductivity from the experimental in-plane electrical conductivity, resulting in the modification of Equation S1 to Equation S2.…”