Dissertation/Thesis Abstract

Synthesis and Thermoelectric Properties of Lanthanum-filled and Heavy-element Transition Metal Doped CoSb3-Based Skutterudites
by Cortez, Araseli, M.S., California State University, Long Beach, 2019, 95; 22615717
Abstract (Summary)

Thermoelectric (TE) materials offer promising potential for power generation and refrigeration applications via a Seebeck effect and Peltier effect, respectively. However, the wide commercialization of TE materials is hindered by its underperforming efficiency that can meet cost effective standards. There is an abundance of work dedicated to improving TE materials by means of optimizing electronic and thermal properties that contribute to its figure of merit, ZT. This project specifically focuses on TE materials known as skutterudites, which fall under the class of Zintl’ compounds. By following a Zintl’ electron count, this work reports the synthesis of a series of skutterudites with nominal composition La0.2+x/3Co4-xBxSb12, where B= Ru,Os. The goal of this approach is to enhance the filling fraction limit of trivalent rare-earth in the skutterudite phase by doping at the metal site with divalent metals and maintaining charge balance. Rare-earth filler atoms act as point defect centers and doping at the metal site contributes to disorder in the structure. Both of these characteristics diversify scattering mechanisms and can reduce thermal conductivity while improving electronic properties. By using larger effective masses, the Seebeck coefficient can be improved and thus maximize zT. All compounds were synthesized by extended annealing and spark plasma sintering. Phase characterization was conducted by means of powder x-ray diffraction, scanning electron microscopy, and electron probe microanalysis. A custom Hall effect and high temperature Seebeck coefficient measurement systems were used for electronic transport data. Thermal conductivity was measured via thermal diffusivity methods. All properties were combined to determine zT.

Indexing (document details)
Advisor: Derakhshan, Shahab
Commitee: Bux, Sabah K, Li, Lijuan, Bu, Xianhui
School: California State University, Long Beach
Department: Chemistry and Biochemistry
School Location: United States -- California
Source: MAI 81/4(E), Masters Abstracts International
Subjects: Chemistry
Keywords: electron-counting, Skutterudites, Spark Plasma Sintering, Thermoelectrics, Zintl' compoounds
Publication Number: 22615717
ISBN: 9781687954350
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