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High temperature transport properties of lead chalcogenides and their alloys

Citation

Wang, Heng (2014) High temperature transport properties of lead chalcogenides and their alloys. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:05292014-133349910

Abstract

This thesis describes a series of experimental studies of lead chalcogenide thermoelectric semiconductors, mainly PbSe. Focusing on a well-studied semiconductor and reporting good but not extraordinary zT, this thesis distinguishes itself by answering the following questions that haven’t been answered: What represents the thermoelectric performance of PbSe? Where does the high zT come from? How (and how much) can we make it better? For the first question, samples were made with highest quality. Each transport property was carefully measured, cross-verified and compared with both historical and contemporary report to overturn commonly believed underestimation of zT. For n- and p-type PbSe zT at 850 K can be 1.1 and 1.0, respectively. For the second question, a systematic approach of quality factor B was used. In n-type PbSe zT is benefited from its high-quality conduction band that combines good degeneracy, low band mass and low deformation potential, whereas zT of p-type is boosted when two mediocre valence bands converge (in band edge energy). In both cases the thermal conductivity from PbSe lattice is inherently low. For the third question, the use of solid solution lead chalcogenide alloys was first evaluated. Simple criteria were proposed to help quickly evaluate the potential of improving zT by introducing atomic disorder. For both PbTe1-xSex and PbSe1-xSx, the impacts in electron and phonon transport compensate each other. Thus, zT in each case was roughly the average of two binary compounds. In p-type Pb1-xSrxSe alloys an improvement of zT from 1.1 to 1.5 at 900 K was achieved, due to the band engineering effect that moves the two valence bands closer in energy. To date, making n-type PbSe better hasn’t been accomplished, but possible strategy is discussed.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:thermoelectric; lead chalcogenide; quality factor; thermal conductivity; scattering mechanism;
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Materials Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Snyder, G. Jeffrey
Thesis Committee:
  • Haile, Sossina M. (chair)
  • Johnson, William Lewis
  • Minnich, Austin J.
  • Snyder, G. Jeffrey
Defense Date:14 May 2014
Non-Caltech Author Email:wangheng83 (AT) gmail.com
Record Number:CaltechTHESIS:05292014-133349910
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:05292014-133349910
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8424
Collection:CaltechTHESIS
Deposited By: Heng Wang
Deposited On:03 Jun 2014 19:27
Last Modified:23 Apr 2015 23:25

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