Award Date

8-1-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics and Astronomy

First Committee Member

Ravhi Kumar

Second Committee Member

Andrew Cornelius

Third Committee Member

Changyong Park

Fourth Committee Member

Michael Pravica

Fifth Committee Member

Rama Venkat

Number of Pages

210

Abstract

Understanding the high-pressure behavior of transport properties has been a driving force in the study of materials under extreme conditions for well over a century being pioneered by P.W. Bridgman in the early 20th century. Research dedicated to the study of these properties leads to a variety of important applications: exploration of insulator to semi-conductor to metal, structural, and electronic phase transitions, correlation of pressure-induced structural phase transitions and the electronic properties along phase boundaries, identifying electronic topological transitions, testing the validity of theoretical models and providing input parameters for calculations at high-pressure and high-temperature conditions, exploration of sample synthesis and behavior of electronic structure at extreme conditions, understanding the effects of chemical pressure when compared to chemical substitution, among a slew of other applications. This work’s main goal was the design and development of a specialized sample cell assembly for use with a Paris-Edinburgh press capable of performing high-pressure and high-temperature (HPHT) electrical resistance, Seebeck coefficient, thermal conductivity measurements alongside energy-dispersive X-ray diffraction and X-ray radiography imaging up to 6 GPa and 500°C to fully characterize the electrical, thermal, and structural properties of materials simultaneously at extreme conditions. This system has been installed at Argonne National Laboratory at the Advanced Photon Source at the Sector 16 BM-B beamline of the High-Pressure Collaborative Access Team and is now available to general users as a measurement technique. The results for pure elemental bismuth and the classical thermoelectric material PbTe are presented to demonstrate the capabilities of the system. With this system, we have also measured the electrical, thermal, and structural properties of SnTe and Mn-doped SnTe thermoelectric materials and the half-Heusler compounds TiNiSn and TiCoSb.

Keywords

Dimensionless Figure of Merit; High-Pressure; Paris-Edinburgh Press; Seebeck Coefficient; Structural Phase Transition; Thermoelectric Materials

Disciplines

Condensed Matter Physics

Language

English


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