Effect of TiO2 on microphase development during phase separation and crystallization in Na2O–B2O3–SiO2 glass system

This study examines the incorporation of TiO₂ into sodium borosilicate glasses and its effect on the formation of glassy and crystalline microphases. Glasses in the composition range: 7Na₂O–23B₂O₃–(70 - X)SiO₂–XTiO₂ (where X = 0–14.6 mol.% TiO₂) which exhibit phase separation were investigated. Raman studies confirm the formation of two different TiO₂ coordinations depending on the molar content of TiO₂. Thermal properties of glasses are unaffected by TiO₂ addition. The domain size of microphase development in TiO₂-containing glass indicates competition between phase separation and crystallization. Enrichment of titanium on the interphase between glassy microphases reduces the mass transfer and consequently limits the growth rate of glassy phases. This competes with the formation of anatase for which a nucleation-controlled mechanism is proposed.