Masters Theses

Date of Award

8-2018

Degree Type

Thesis

Degree Name

Master of Science

Major

Biomedical Engineering

Major Professor

Jacqueline A. Johnson

Committee Members

Russell L. Leonard, Feng-Yuan Zhang

Abstract

For this work, a fluorochlorozirconate thin film storage phosphor was developed in a two-step process. In the first step, the synthesis and characterization of the glass portion of the storage plate was completed. The second step incorporated crystalline and dopant materials into the glass matrix to develop the glass-ceramic thin film. After synthesis was completed, characterization was conducted, including measurement of photostimulated emission after prior x-ray irradiation indicating the ability of the thin film to act as a storage phosphor plate.The presence of reduced zirconium in fluorozirconate (FZ) glasses is highly unfavorable due to its detrimental effect on glass quality. Previous researchers have relied upon the use of a fluorine-containing processing gas to prevent the reduction of zirconium in FZ glasses deposited as thin films by pulsed laser deposition (PLD). However, the use of a fluorine-containing processing gas as an oxidizing agent is disadvantageous, due to its toxicity. Eliminating the need for the processing gas would lead to a significantly safer and simpler process. The approach presented within this thesis is to incorporate indium, which is multivalent, into the PLD ablation target in order to stabilize the zirconium and remove the need for a processing gas. Using a fluoride glass target, FZ glass films were successfully deposited on fused silica substrates by PLD, without the need for any processing gas.In computed radiography applications using conventional granular storage phosphor materials, scattering of the stimulating laser light during read-out leads to decreased spatial resolution. The desire for high spatial resolution has led to imaging plates with thinner phosphor layers in order to reduce this scattering. The films produced in this study consist of multiple transparent layers of orthorhombic phase barium chloride nanocrystals doped with europium, separated by nanoscale layers of fluoride glass. The transparent nature of these films reduces blurring of the image due to scattering of the stimulating light during read-out. The films are deposited on fused silica substrates via pulsed laser deposition, utilizing a multicomponent target. This method allows for a higher concentration of luminescent centers compared to glass-ceramic imaging plates synthesized in bulk form.

Comments

A portion of this document was originally published by C.W. Bond, R.L. Leonard, R.A. Erck, A.Y. Terekhov, A.K. Petford-Long, and J.A. Johnson in the Journal of Non-Crystalline Solids: Bond, C. W., Leonard, R. L., Erck, R. A., Terekhov, A. Y., Petford-Long, A. K., & Johnson, J. A. (2018). Pulsed laser deposition of transparent fluoride glass. Journal of Non-Crystalline Solids, 488, 19-23. doi:10.1016/j.jnoncrysol.2018.03.005

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