The p-n conduction type transition in Ge-incorporated Bi2Te3 thermoelectric materials
Journal
Acta Materialia
Journal Volume
122
Start Page
120
End Page
129
ISSN
13596454
Date Issued
2017
Author(s)
Abstract
The capability of converting waste heat into electricity characterizes the technology of thermoelectricity as a feasible solution in dealing with the energy issue. The Bi2Te3-based alloys have long been in the spotlight as they show promising zTs and high thermal stability near the room-temperature region. Herein, the experimentally determined 523 K isothermal section of ternary Bi-Ge-Te system concludes that the four ternary compounds, the Ge3Bi2Te6, the Ge1.5Bi1.5Te5, the Ge1Bi2Te4 and the Ge1Bi4Te7, are thermally stabilized and the solubility of Ge in Bi2Te3 could reach ∼5.0 at.%Ge. The thermoelectric performance of various Ge-incorporated Bi2Te3 alloys with compositions of Bi40-yGexTe60-x+y (x = 0–12.5, y = 0–10.0) are evaluated within 300 K-650 K. The conduction type of those alloys transits from p-type, for the un-doped Bi2Te3, to n-type semiconducting as one of the following conditions are satisfied: (1) the concentration of Te drops to less than 60.0 at.%, or (2) the concentration of Te exceeds 60.0 at.% and the ratios of Ge/Bi is larger than 0.2. The zT peak values reach zT∼0.9 at 325 K for p-type alloy P2 (Bi39.0Ge1.0Te60.0), which features a Bi2Te3 single-phase microstructure, and zT∼0.45 at 525 K for n-type alloy N5 (Bi32.5Ge10Te57.5), which falls in a Bi2Te3+Ge1Bi2Te4+Te three-phase region, respectively. © 2016 Acta Materialia Inc.
Subjects
Bi2 Te3
Isothermal section
p-n transition
Thermoelectric materials
zT
Publisher
Elsevier Ltd
Type
journal article