Date of Award

12-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Committee Member

Dr. Joseph W. Kolis, Committee Chair

Committee Member

Dr. Shiou-Jyh Hwu

Committee Member

Dr. William T. Pennington

Committee Member

Dr. Joseph S. Thrasher

Abstract

The crystal growth of large, defect-free and optically transparent materials has been an active area of research for over two centuries. A multitude of crystal growth techniques have been employed during this time, each submitting advantages and disadvantages to the solid-state community. As the heart of solid state lasers, communication devices and semiconductors, synthetically grown crystals for optical and magnetic applications hold the key for future innovation and design. There are large classes of materials that display recumbent characteristics that inhibit their manipulation by most current solid state techniques on the market. These refractory oxides display extreme melting ranges (> 2000 ⁰C), which inhibit solubility in the melt-based solid-state techniques typically engineered in crystal growth laboratories. Herein, this dissertation employs the high temperature and high pressure technique to drive the solubility of select refractory oxides into solution several hundred degrees prior to the melting point being attained. The investigation of pentavalent and tetravalent oxides (Nb2O5, Ta2O5, TiO2, GeO2, and SiO2) with rare-earth oxides (La - Lu, Sc) under hydrothermal conditions has led to the discovery of several new compounds previously unattainable by conventional solid-state growth techniques. These included, but are not limited to, RENbO4 (RE = La-Lu), La5Ti4O15(OH), Lu5Ti2O11(OH), and Ba2Lu2Si4O12F2 single crystals. The discovery of new classes of materials will lead to further investigation of optical properties. Furthermore, the ability to solubilize metal oxides, hundreds of degrees below their melting point, is leading to high-quality, defect-free, bulk single crystal growth of new and existing materials. As the solution chemistry of metal oxides continues to be investigated and explored under hydrothermal conditions, new optical and magnetic materials continue to emerge and display desirable traits in applied sciences.

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