NMR Studies of Strontium Zinc Silicate Based Glass/Glass-Ceramic Sealants for High Temperature Applications

Glass having composition 40SrO-10ZnO-40SiO(2)-2B(2)O(3)-2Al(2)O(3)-2TiO(2)-2Cr(2)O(3)-2Y(2)O(3) (mol%) was prepared by melt-quench technique and converted into glass-ceramics by controlled crystallization. Formed crystalline phases in glass-ceramics were identified using powder XRD. MAS-NMR spectroscopy shows the presence of mainly Q(1) and Q(2) silicate structural units and BO3 structural units of boron in the glass network. It is inferred from Si-29 NMR and XRD that glass-ceramics have high crystallinity and during crystallization initially Sr2ZnSi2O7 crystalline phase is formed and later SrSiO3 crystalline phase is crystallized. B-11 and Al-27 MAS-NMR of glass-ceramics depict an increase in the BO4 and AlO4 structural units with the crystallization. In accordance with XRD, NMR results also suggest the formation of solid solution of Sr2ZnSi2O7 phase with substitution of Zn/Si tetrahedral sites with B/Al.