Date of Award

1-1-2010

Document Type

Campus Access Dissertation

Department

Chemistry and Biochemistry

Sub-Department

Chemistry

First Advisor

Hans Conrad Zur Loye

Abstract

The act of materials discovery continues to grow in importance, as new materials are needed for a variety of applications ranging from solar panels to solid-state lighting. Many research groups have focused their efforts on discovering new materials, specifically oxides, where the process is being fine tuned to yield compounds with unusual or enhanced physical properties. While the traditional solid-state method is very practical for the preparation of large quantities of materials, the high temperature solid-state approach tends to produce the most thermodynamically stable product, thus limiting the discovery of new materials. Alternative synthetic routes have been explored to overcome this limitation and to gain access to new and unusual compounds.

One method, the crystal growth from high temperature solutions, has proven to be an excellent route for material discovery, in particular for generating high quality single crystals of complex oxides. Our group has been very successful at utilizing molten carbonates and hydroxides to prepare crystals of new complex oxides that incorporate a wide variety of different metals. Specifically, molten hydroxides have proven to be ideal for the dissolution and subsequent recrystallization of niobium, tantalum and iron-containing oxides and several new complex oxides were prepared during this study. These materials were structurally characterized and their optical properties were investigated. Single crystals of complex oxides of uranium, on the other hand, have proven to be more difficult to grow using the hydroxide fluxes, prompting a switch to molten carbonates, which have readily yielded new quaternary uranium-containing phases. This study focuses on the synthesis, the structural characterization and the optical properties of novel niobium, tantalum and iron-containing oxides as well as highlights the development of a new synthetic approach for the preparation of complex uranium oxides.

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