Chemistry Letters, Vol.35, No.11, 1268-1269, 2006
Structural change around Si atoms in P2O5-SiO2 binary glasses before and after annealing by Si-29 MAS NMR spectroscopy
The Si-29 MAS NMR spectra of P2O5-SiO2 binary glasses were measured before and after annealing to examine the local structure around Si atoms in the glasses. The glasses were composed of SiO6 octahedra and Q(4) (SiO4 tetrahedra with four bridging oxygens). By increasing the P2O5 content, the fractions of SiO6 octahedra increased and those of Q4 decreased. The fractions of SiO6 octahedra increased by 6-8% in the range of 29.7 to 47.4 mol % P2O5 by annealing for 5 h. This result was found for the first time in binary glasses. On the basis of the results obtained, the local structure around Si atoms in the glasses and the structural change by annealing are discussed.