Fig. 3

Stacked ²⁹Si NMR data for NS4 glass at various Ti concentrations, normalized by integrated intensity. The two predominant peaks are the Q³ and Q⁴ peaks at − 93 and − 106 ppm, respectively. At 0% TiO₂, the two peaks account for nearly equal areas under the curve, as is expected for NS4 glasses with 50% Q³ Si and 50% Q⁴ Si. There is a shift in peak position of the Q⁴ to higher frequency with addition of Ti to the NS4 glass, whereas the Q³ peak is negligibly affected by the addition of Ti. The shift in Q⁴ to higher frequency is likely the result of Ti nearest neighbor effects on the Q⁴ Si. Open circles are fitted peak centers