Date of Award

Summer 8-2011

Degree Type

Dissertation-Restricted

Degree Name

Ph.D.

Degree Program

Engineering and Applied Science

Department

Physics

Major Professor

Stokes, Kevin

Second Advisor

Spinu, Leonard

Third Advisor

Zhou, Weilie

Fourth Advisor

Schilling, Paul

Fifth Advisor

Poudeu, P. Ferdinand

Abstract

Thermoelectric materials convert temperature gradients into electricity and vice-versa. These materials utilize the Seebeck effect for power generation and function without moving parts and are highly reliable. The efficiency of thermoelectric devices is related to the dimensionless figure of merit for the constituent materials, defined as where S is the Seebeck coefficient, is the electrical conductivity, is the thermal conductivity and T is the temperature. Maximizing ZT is very challenging because of interdependence of parameters, for example, increasing the electrical conductivity by increasing the carrier concentration invariably lowers S and vice versa. Presently numerous thermoelectric materials are being investigated by different research groups. Despite having high thermal conductivity, half-Heusler materials are promising candidates for thermoelectric applications due to their relatively high power factor () and the ability to tune the thermal and electrical properties through substitutional doping. 2S

In this research work, I have investigated the synthesis and transport properties of half Heusler series Zr 0.5Hf0.5Ni1-xPdxSn0.99Sb0.01 (0≤x≤1). Also the role of NiO and HfO2 nanoinclusions in half –Heusler matrix were studied. The half Heusler samples were prepared by solid state reaction. Resistivity, Seebeck coefficient and thermal conductivity were measured for all samples over a temperature range from room temperature to 750K. Hall effect measurements at room temperature were also performed. Addition of NiO inclusions did result in an improvement in ZT whereas addition of 3% vol HfO2 in Zr0.5Hf0.5Ni0.8Pd0.2Sn0.99Sb0.01 showed 19% improvement in ZT.

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The University of New Orleans and its agents retain the non-exclusive license to archive and make accessible this dissertation or thesis in whole or in part in all forms of media, now or hereafter known. The author retains all other ownership rights to the copyright of the thesis or dissertation.

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