Doping of a high calcium oxide metaphosphate glass with titanium dioxide

Abstract

This study investigates the effect of doping a high calcium oxide containing meta-phosphate glass series (CaO)40(Na2O)10(P2O5)50 with TiO2 (1, 3, and 5 mol %). TiO2 incorporation increased the density and glass transition temperature while reduced the degradation rate (5 mol% in particular) by two folds compared with (CaO)30 system reported previously. This has been confirmed by ion release and the minimal pH changes. TiP2O7, NaCa(PO3)3 and CaP2O6 phases were detected for all TiO2 containing ceramics. XPS showed that the surface is composed of Ca, P, and Ti. Ti was recognised mainly as TiO2, but its total amount was lower than theoretical values. 31P magic angle spinning (MAS) NMR showed a downfield shift of the 31P lineshape with increasing TiO2, interpreted as an effect of the titanium cation rather than an increase in the phosphate network connectivity. FTIR showed that incorporation of TiO2 increased the strength of the phosphate chains, and the O/P ratio while introducing more Q1 units into the structure at the expense of the Q2 units. There were no differences, however, in surface topography roughness and free energies between these glasses. These results suggested that TiO2 and CaO were acting synergistically in producing glasses with controllable bulk and structural properties.