Crystallisation And Viscosity Of Phosphate Melts In The System Na20-Ca0-Mg0-P205-Al203-Ti02

Glasses in the system Na20-Ca0-Mg0-P205-Al203-Ti02 were studied with respect to their crystallisation and viscosity. Glasses in the metaphosphate range are composed of phosphate chains, and possess a comparable small tendency to crystallisation. Here, A1PO4 in a crostobalite-like modification and Ca2P207 are formed. Glasses in the intermediate range between metaphosphate and invert glass structures are composed of smaller phosphate units and show higher crystal growth velocities as well as higher viscosities. Additions of MgO, Al203 and Ti02 result in a strengthening of the glass network and hence, increasing viscosities and a notably smaller tendency to crystallisation.