Nuclear Magnetic Resonance Investigations of Structural Phase Transitions in Silicon Dioxide Cristobalite and Tridymite and Related Phases PDF Download

Author: Yuehui Xiao
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Languages : en
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Book Description
This thesis contributes to the application of nuclear magnetic resonance (NMR) techniques in studying structural phase transitions (SPT's) of the SiO$sb2$ cristobalite and SiO$sb2$ and AlPO$sb4$ tridymite polymorphs. The structural properties and SPT's of these phases have been of mineralogical, physical and industrial interest for decades. However, the microscopic characteristics of the SPT's and the origins of the commonly observed structural disorder in the high temperature phases have been poorly known. NMR techniques call provide important information concerning the temperature variation of the short-range structural parameters through SPT's. Moreover, the dynamical behavior of high temperature phases in the NMR frequency range ($sim$1-500 MHz) can sometimes be uniquely elucidated by relaxation rate measurements and spectral simulation. The work presented here includes in situ high temperature $sp{29}$Si, $sp{31}$P and $sp{27}$Al NMR results for cristobalite (Chapter II), chemically stabilized $beta$-cristobalite (Chapter III), various tridymite polymorphs (MC and PO, Chapter IV; MX-1 Chapter V; AlPO$sb4,$ Chapter VI) and a spin-lattice relaxation investigation of the dynamic properties for the high temperature SiO$sb2$ and AlPO$sb4$ tridymite phases (Chapter VII).