Nuclear magnetic resonance studies of alkaline earth phosphosilicate and aluminoborosilicate glasses

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.