Date of Award

1-1-2013

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

Sub-Department

Chemistry

First Advisor

Thomas Vogt

Abstract

In this dissertation, the structure and photoluminescent properties of A3MO4F-type materials (A = Sr, Ba, Ca; M =Al, Ga, In, Si, Ge) are studied as potential phosphors for compact fluorescent lamps (CFLs) and phosphor converted light emitting diode (pc LED) lights. Chapter 1 outlines background information of the evolution of lighting technology as well as detailing the synthesis, structural characterization and photoluminescence measurements. Chapter 2 focuses on the changes that the Sr3AlO4F structure undergoes as a result of exposure to a 5% H2/95% Ar atmosphere. High-resolution neutron powder diffraction is used to probe for minute structural changes. Chapter 3 is a detailed study of the isovalent substitution of Sr2+ by Ba2+ and Ca2+ at the A site in Sr3 xAxGaO4F. In this study, changes in bond valence sums, global instability indices, and photoluminescent properties are related as a result of these substitutions. As the Ba2+ content increases in Sr3 xAxGaO4F, the global instability indices decrease. Conversely, Ca2+ substitution in these materials causes the global instability indices to increase. Chapter 4 focuses on substitutions at the M-site of the host structure, where the M-site contains Al3+, Ga3+, and In3+. These substitutions at the M site allow us to tailor the photoluminescence of A3MO4F-type materials for potential use in UV-LED lights. In chapter 5, Sr3GaO4F is doped with Ce3+ and Na+ to determine the critical concentration with respect to quenching. After identifying the critical concentration for radiationless quenching, aliovalent substitutions of Ga3+ by Si4+ and Ge4+ are made at the M site and their effect on the PL emission is studied. Significant photoluminescence intensity is seen when ëex = 450 nm in the Ce3+ substituted Sr3GaO4F structure, which allows for these materials to become potential LED phosphors.

Rights

© 2013, Robert Lenwood Green

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