Senior Honors Projects, 2010-current

Date of Award

Spring 2015

Document Type

Dissertation/Thesis

Degree Name

Bachelor of Arts (BA)

Department

Department of Physics and Astronomy

Advisor(s)

Costel Constantin

Abstract

In this work, the thermoelectric properties of Beta-MnO2 powders as a function of electrical resistance are measured and compared to theoretical models. The discovery of a giant Seebeck coefficient by Song et al. in these powders rejuvenated interest in understanding the physical mechanism behind it. A simple pestle and mortar method was used to modify the MnO2 powder sizes. We and the largest S coefficient, power factor, and thermal conductivity values were found to be S=-316 uV/K, (sigma)S2 =5.8x10-7 W/mK2 and k=0.2096 W/(mK), all observed at a particle electrical resistance of R=9.8 Ohms. From these values the highest figure of merit was observed to be ZT=3.28x10-4. Ab initio density functional theory and non-equilibrium Green's functions method with a local density approximation was used to simulate the thermoelectric properties of MnO2 nanowires. The power factors obtained from theory and experiment are within the same order of magnitude, which implies that power factor remains constant independent of particle size. Based on the experimental and theoretical evidence, a model for the formation of micrometer size MnO2 conglomerates is proposed.

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