Structural characterization of some sol–gel derived phosphosilicate glasses

• Triethyl-phosphite/phosphate (TEP) and H3PO4 were P-sources to obtain 10P2O5–90SiO2.
• Spectral data by NMR, Raman, XPS and XRF was obtained for these gels and glasses.
• Un-hydrolyzed TEP in gel underwent partial vaporization and degradation by annealing.
• A 1.84 higher P2O5/SiO2 ratio was found for the H3PO4 derived glass than TEP one.

A comparative study of three phosphosilicate gels of the 90SiO2–10P2O5 composition obtained from tetraethoxysilane and three phosphorous precursors: triethylphosphate (TEP), triethylphosphite (TEPI) and H3PO4 is performed. 29Si and 31P Magic Angle Spining NMR, X-ray Photoelectron, X-ray Fluorescence and Raman spectroscopies as well as TG analysis are used in order to establish phosphorous precursors and annealing influence on composition and structure of the outcome materials. Unlike the three dimensional silicate network made of Si(OSi)x(OH)4−x species, unreacted TEP (100% Q1 condensed phosphorous units) from TEP derived gel and a large amount of isolated phosphorous species (39.7% Q0) in the H3PO4 derived gel are identified. Annealing at 700 °C of the three gels give similar structure with the 90SiO2–10P2O5 glass, excepting the triethylphosphate derived glass that has a much lower P content. Thus, the H3PO4 derived glass at 700 and 1000 °C shows 1.89 and 1.94 times higher P2O5/SiO2 ratios than in the case of the TEP derived one.

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