The present dissertation investigates the relationship between the structure and thermoelectric properties of ZnO based materials, with a focus on trivalent element doping on engineering the microstructure and altering the electrical and thermal transport properties. Within the solubility range, the addition of trivalent elements, such as In3+, Fe3+ and Ga3+, is observed to increase the electrical conductivity of ZnO and decrease the thermal conductivity. / Engineering and Applied Sciences

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We use normal mode decomposition to obtain phonon properties from quasi-harmonic lattice dynamics calculations and classical molecular dynamics simulations in unstrained Lennard-Jones argon superlattices with perfect and mixed interfaces. Debye scaling of phonon lifetimes at low frequencies in both perfect and mixed superlattices and Rayleigh scaling for intermediate frequencies in mixed superlattices is observed. For short period mixed superlattices, lifetimes below the Ioffe-Regel limit are observed. The relaxation-time approximation of the Boltzmann transport equation is used to predict cross-plane and in-plane thermal conductivity. We find that using a dispersion relation which includes the secondary periodicity is required to predict thermal conductivity. The assumption of perturbative disorder, where Tamura elastic mass defect scattering theory can be applied, was found to be valid for predicting cross-plane thermal conductivities but not in-plane thermal conductivities in mixed superlattices.

We use normal mode decomposition to obtain phonon properties from quasi-harmonic lattice dynamics calculations and classical molecular dynamics simulations in unstrained Lennard-Jones argon superlattices with perfect and mixed interfaces. Debye scaling of phonon lifetimes at low frequencies in both perfect and mixed superlattices and Rayleigh scaling for intermediate frequencies in mixed superlattices is observed. For short period mixed superlattices, lifetimes below the Ioffe-Regel limit are observed. The relaxation-time approximation of the Boltzmann transport equation is used to predict cross-plane and in-plane thermal conductivity. We find that using a dispersion relation which includes the secondary periodicity is required to predict thermal conductivity. The assumption of perturbative disorder, where Tamura elastic mass defect scattering theory can be applied, was found to be valid for predicting cross-plane thermal conductivities but not in-plane thermal conductivities in mixed superlattices.

Thesis (Ph. D.)--University of Oregon, 2007. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 209-231). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (doctoral)--University of Oulu, 2008. / Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--University of Oregon, 2004. / On t.p. "m̲" and "n̲" are subscript. Typescript. Includes vita and abstract. Includes bibliographical references (leaves 147-153). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 35-37). Also available in electronic version. Access restricted to campus users.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 179-190). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 179-190). Also available on the Internet.