Structure and properties of titanium-zinc borophosphate glasses

The structure of 50ZnO-10B₂O₃-40P₂O₅+xTiO₂ glasses prepared by slow cooling (for x=0-24 mol% TiO₂) or by quenching (for x=28-64 mol% TiO₂) was studied by Raman, ³¹P and ¹¹B MAS NMR spectroscopy. TiO₂ incorporates into the glass structure, which results in a decrease in the molar volume and an increase in the glass transition temperature. According to Raman spectra Ti atoms form distorted TiO₆ octahedra and their incorporation into the structural network results in the depolymerization of phosphate chains. ¹¹B NMR spectra of the glasses with increasing TiO₂ content show gradual changes from one symmetrical signal of B(OP)₄ units to a broad complex signal which was separated into five signals ascribed to four different types of BO₄ units and one BO₃ unit. With increasing TiO₂ content a part of boron atoms changes from tetrahedral BO₄ to trigonal BO₃ units, which is ascribed to the formation of TiO₆ units in the glass structure.