Fig. 7

Three different mechanisms by which ^[4]Ti can be incorporated into the glass structure include: a in replacement of Q³ Si, which would induce a loss of Q³ Si and growth of Q⁴ Si in the NMR spectra, which is not observed, b for Q4 Si in the network with no adjacent Q3 Si, which would incite the growth of an additional Q4 peak at a slightly higher energy than the primary Q4 peak, and c for Q4 Si adjacent to Q3 Si, which would incite a peak shift toward higher frequency of the Q3 Si peak. The latter is not observed in the NS8 glasses, but a slight shift in peak position is detectable in the NS4 glasses (Fig. 3)