Solid-State Nuclear Magnetic Resonance Studies of Quadrupolar Nuclei in Inorganic Systems (Nmr)
Timken, Hye Kyung Cho
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https://hdl.handle.net/2142/70381
Description
Title
Solid-State Nuclear Magnetic Resonance Studies of Quadrupolar Nuclei in Inorganic Systems (Nmr)
Author(s)
Timken, Hye Kyung Cho
Issue Date
1987
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Physical
Abstract
Solid-state nuclear magnetic resonance (NMR) has been used to study a variety of systems of chemical, physical, and geological interest, including zeolites, metasilicates, and semiconductors. Among the nuclei studied were $\sp $O, $\sp{27}$Al, $\sp{69}$Ga and $\sp{71}$Ga. The general motivations for this research were to broaden solid-state NMR into new nuclei, especially quadrupolar nuclei, and to examine how quadrupolar NMR can be used as a structural tool. The research involved several applications, brief descriptions of which are presented below.
Quadrupolar echo techniques were applied in order to resolve chemically non-equivalent sites in solids which have nearly identical chemical shifts. Oxygen-17 NMR studies of zeolites and related systems demonstrated that the $\sp $O NMR spectra of these systems consist of resonances from chemically distinct oxygen species, Si ($\sp $O) Si and Si ($\sp $O) Al for aluminosilicates; Si ($\sp $O) Si and Si ($\sp $O) Ga for gallosilicates; and Al ($\sp $O) P for the AlPO$\sb{4}$ zeolite analogs. From $\sp{69}$Ga and $\sp{71}$Ga NMR studies of gallium analog zeolites we have characterized the framework gallium sites (Ga(OSi)$\sb{4}$), and have obtained NMR parameters essentially by carrying out a "frequency dependence" study at one magnetic field strength by observing the different apparent chemical shifts of $\sp{69}$Ga and $\sp{71}$Ga. We have measured and interpreted the variable-temperature spin-lattice relaxation times (T$\sb{1}$) of $\sp{27}{\rm Al}$ in zeolites. The major relaxation mechanism is due to the quadrupolar interaction. For hydrated zeolites, the motions of the hydrated water in zeolites gives rise to a fluctuating electric field gradient at the framework Al nuclear sites. From $\sp $O NMR studies of a series of alkaline earth metasilicates, we have characterized the different oxygen sites encountered (one bridging oxygen and two distinct non-bridging oxygens). Finally, we have applied $\sp{69}$Ga and $\sp{71}$Ga NMR to a series of gallium-containing III-V semiconductors. By applying the magic-angle sample-spinning technique, we can selectively remove some specific linebroadening mechanisms and the contribution of each mechanism (dipolar, first-order and second-order quadrupolar, pseudodipolar, and exchange interaction) may be more accurately estimated.
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