Date of Award

8-2009

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Chemistry

Advisor

Kolis, Joseph W

Committee Member

Ballato , John

Committee Member

DesMarteau , Darryl

Committee Member

Pennington , William

Abstract

Large single crystals of alkali metal fluorides are desirable for many reasons. Fluoride laser crystals have a wide transmission range and on account of their low phonon energies, many efficient laser emissions have been obtained from 285 nm to 4.34 µm.1,2 Inorganic fluoride single crystals feature large bandgaps, very wide optical transmittance ranges from vacuum-ultraviolet (VUV) to mid-IR wavelength regions, lower refractive indices than those of oxides, and typically lower phonon energies (which drastically reduce multiphonon relaxation rates of rare earth ions).3
The main goal of this work was to investigate the hydrothermal synthesis of alkali metal fluorides. Melt techniques have been used thoroughly to research a variety of fluoride systems and showed many phases that were inaccessible due to incongruent melting or phase stability. The existence of these phases was shown but never characterized or grown as a crystalline material. Solution growth in supercritical water was an ideal way to attempt the synthesis of novel compounds and phases. New synthetic routes to known phases and compounds also arose as a part of this work.
Optically clear colorless crystals of K2BeF4 were synthesized up to 2 mm in size, and showed no phase transitions up to 1029 K, which suggests paraelectricitys at room temperature, contradicting previous reports.4 Attempts to incorporate a rare earth ion into the fluoroberyllate lattice proved unsuccessful however reactions between beryllium fluoride and lanthanide fluorides could be exploited as a synthetic route to single crystal rare earth fluorides.
Hydrothermal reactions with KF produced crystals of three different phases: hexagonal KY2F7, trigonal KYF4 and orthorhombic K2YF5. All were optically clear, colorless crystals, with the K2YF5 crystals growing the largest. This compound is beneficial due to its application as a radiation dosimeter and laser host.5,6 Optical quality colorless crystals of RbY2F7 and CsY2F7 up to 4 mm in size were produced, and many spectroscopically active rare earth elements were doped into both hosts. A novel synthetic pathway to the hexagonal β-RbGd3F10, was discovered which led to the novel compound, β-RbHo3F10. The hydrothermal synthesis of hexafluoroelpasolites and lanthanide sesquioxides is also investigated. The hydrothermal synthesis described in this work has furthered the study of complex fluorides for optical applications. Novel synthetic pathways were discovered to known optical materials. Novel materials were also discovered.
References
1) Takashima, M. In Advanced Inorganic Fluorides: Synthesis, Characterization and Applications, Nakajima, T.; emva, B.; Tressaud, A.; Elsevier: Amsterdam, The Netherlands, 2000, 176.
2) Fouassier, C. In Advanced Inorganic Fluorides: Synthesis, Characterization and Applications, Nakajima, T.; emva, B.; Tressaud, A.; Elsevier: Amsterdam, The Netherlands, 2000, 316.
3) Capper, P. In Bulk Crystal Growth of Electronic, Optical and Optoelectronic Materials, John Wiley and Sons: Great Britain, 2005.
4) Solans, X.; Gonzalez-Silgo, C.; Calvet, T.; Ruiz-Perez, C.; Martinez-Sarrion, M. L.; Mestres, L. Phys. Rev. B 1998, 57(9), 5122-5125.
5) Azorin-Nieto, J.; Khaidukov, N.M.; Sanchez-Rodriguez, A.; Azorin-Vega, J.C. Nuclear Instruments and Methods in Physics Research, 2007, B263, 36-40.
6) Wang, D.; Min, Y.; Xia, S.; Makhov, V.N.; Khaidukov, N.M.; J.C. Krupa, J.C. Journal of Alloys and Compounds, 2003, 361, 294-298.

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