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.