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DOI: 10.1039/A705465C (Paper) Reference Section for: J. Mater. Chem., 1998, 8, 165-169

31P and 29Si NMR study of sol–gel-synthesized phosphate ceramics

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Li-qiong Wang, William D. Samuels, Gregory J. Exarhos, Burtrand I. Lee and Zhicheng Cao

Abstract

31P and 29Si solid-state magic angle spinning (MAS) and liquid-state nuclear magnetic resonance (NMR) techniques have been applied to the study of sol–gel-synthesized phosphate ceramic composites. This study emphasizes the chemistry and structural properties for both sols and gels prepared by directly reacting P2O5 with tetraethoxysilane (TEOS). This new method of formation of both the sols and gels is a drastic improvement in the retention of phosphorus during the formation of the phosphosilicate gels, and it provides a lower temperature route to six-coordinate silicon. Both31P and 29Si liquid-state NMR spectra for sols prepared without water showed the presence of P–O–Si bonds. The 31P NMR spectra for sols prepared with water resembled those for the PO(OH)x(OR)3–xprecursors, while29Si NMR spectra indicated that TEOS had undergone partial hydrolysis and condensation. Hexacoordinated silicon was observed for the first time in gels prepared at low temperature (70 °C). P–Si gels prepared directly by using P2O5 were compared with those using other molecular precursors.

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