Materials Discovery by Crystal Growth: Synthesis, Structure Determination, Magnetic, and Optical Properties of Complex Lanthanide Containing Oxides, Oxyhydroxides, and Oxyfluorides

Author

Allison Marie Latshaw, University of South Carolina

Date of Award

2016

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

Sub-Department

College of Arts and Sciences

First Advisor

Hans-Conrad zur Loye

Second Advisor

Daniel Reger

Abstract

Exploratory crystal growth is a versatile technique and one that can advance materials discovery. Through exploratory crystal growth, it is possible to synthesize many new materials that can have applications in many fields, including solid-state lighting. There exist many adaptations for exploratory crystal growth, including the use of alkali halide flux growth and hydroflux growth, both reported herein. By changing variants in these techniques like reactant ratios, temperature, reaction profile, and, most importantly here, the flux compositions, it is possible to change the products formed or fine tune reactions for product purity.

For solid-state lighting applications, compounds that adopt colorless frameworks, like tungstates, germanates, and silicates are of interest. Herein, we report on the synthesis, structure determination and physical property measurements of Na₅Ln(OH)₆WO₄ (Ln = Er, Tm, Yb), Na₅Ln₄F[GeO₄]₄ (Ln = Pr, Nd), Na_xLn_10-x(SiO₄)₆O_{2- y}F_y, Ca_xLn_10-x(SiO₄)₆O_2-yF_y (Ln = Nd, Sm, Eu, Gd), Gd_9.34(SiO₄)₆O₂, K_1.32Pr_8.68(SiO₄)₆O_1.36F_0.64, Na₅Ln₄F[SiO₄]₄ (Ln = Pr, Nd, Sm-Tm), K₅Pr₄F[SiO₄]₄, K₃LnSi₂O₇ (Ln = Sm, Y), Na₃LnSi₂O₇ (Ln = Ho, Yb), NaLnSiO₄ (Ln = La, Yb), K₅Ln₂Si₄O₁₃F (Ln = Y, Sc), and Cs₃LnSi₄O₁₀F₂ (Ln = Gd, Tb, Dy). These new compositions have been studied for magnetic properties, second harmonic generation, and optical properties, including fluorescence quantum yield, when practical.

Antiferromagnetic ordering has been observed in Na₅Tb₄F[SiO₄]₄ and Na₅Dy₄F[SiO₄]₄. The Na₅RE₄F[SiO₄]₄ (RE = Pr, Sm-Tm) series exhibits second harmonic generation and fluorescence has been observed in NaEu₉(SiO₄)₆O₂, Na_1.5Eu_8.5(SiO₄)₆OF, Eu_9.34(SiO₄)₆O₂, Gd_9.34(SiO₄)₆O₂, Na₅Eu₄F[SiO₄]₄, Na₅Gd₄F[SiO₄]₄, Na₅Tb₄F[SiO₄]₄, and K₃YSi₂O₇. Fluorescence quantum yield was measured on Na₅Eu₄F[SiO₄]₄, Na₅Gd₄F[SiO₄]₄, and Na₅Tb₄F[SiO₄]₄. The optical properties are exciting as they indicate that a silicate material, composed of the earth abundant element silicon, may be able to be used as a framework for new potential phosphor coatings for light emitting diodes (LEDs). Using silicate materials as new host structures could decrease the cost of LEDs.

Rights

© 2016, Allison Marie Latshaw

Recommended Citation

Latshaw, A. M.(2016). Materials Discovery by Crystal Growth: Synthesis, Structure Determination, Magnetic, and Optical Properties of Complex Lanthanide Containing Oxides, Oxyhydroxides, and Oxyfluorides. (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/3878