²⁹Si High Resolution NMR of the Sol‐Gel Chemistry Forming SiO₂ — TiO₂ — ZrO₂ Glasses from Alkoxides

Abstract

Abstract Chemical reaction steps have been monitored by 29 Si NMR in the liquid stage of a sol‐gel process during the preparation of glasses in the ternary system 65SiO 2 —20TiO 2 —15ZrO 2 from the corresponding alkoxides. Most of the recorded signals could be assigned to monomer species and larger building units, and the time evolution of the spectra of the two‐component systems Si/Ti and Si/Zr has been correlated with that of the pure starting material TEOS. No evidence has been found for the formation of ≡Si —O—Ti≡ or ≡ Si —O —Zr≡ bonds in the early polymerization. Quantitative considerations of the 29 Si spectra have revealed the main condensation pathways in the Si/Ti system. 29 Si MAS NMR yields, as a preliminary result, a higher branching of the network when passing from the dried gel to the annealed gel‐glas