Abstract
The 11B, 27Al, 29Si and 31P magic angle spinning (MAS) NMR spectra of MO–P 2O 5, MO–SiO 2–P 2O 5 and MO(M ′ 2O)–SiO 2–Al 2O 3–B 2O 3 (M=Mg, Ca, Sr and Ba, M ′=Na) glasses were examined. In binary MO–P 2O 5 (M=Ca and Mg) glasses, the distributions of the phosphate sites, P(Q n ), can be expressed by a theoretical prediction that P 2O 5 reacts quantitatively with MO. In the ternary 0.30MO–0.05SiO 2–0.65P 2O 5 glasses, the 6-coordinated silicon sites were detected, whose population increases in the order of MgO<CaO<SrO≒BaO. In xCaO–0.05SiO 2–(0.95− x)P 2O 5 glasses, its population increases with an increase in f (=([P 2O 5]−[MO]−[B 2O 3]−[Na 2O])/[SiO 2]) and has maximum at f=9. The signal due to the 5-coordinated silicon atoms is also observed when x is smaller than 0.45. When three network-forming oxides such as SiO 2, Al 2O 3 and B 2O 3 coexist, Al 2O 3 reacts preferably with MO. The populations of 4-coordinated boron atoms, N 4, are expressed well with r/(1− r), where r=([Na 2O]−[Al 2O 3])/([Na 2O]−[Al 2O 3]+[B 2O 3]). The correlation of the Raman signal at 1210 and 1350 cm −1 with the NMR signal of Si(Q 6) at −215 ppm is also seen.
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