CRYSTALLISATION OF CALCIUM PHOSPHATE GLASS CONTAINING VANADIUM OXIDE

The crystallisation behaviour of calcium phosphate glass containing vanadium oxide was studied. Glass with a molar ratio of [CaO]/[P2O5] = 1.13 and a V2O5 content of 8 mol% was prepared. The crystallisation of bulk glass samples was performed under isothermal conditions at T = 650-820 C. The surface crystallisation mechanism of the glass with dendritic growth of the primary alpha-Ca2P2O7 phase was seen. In all the crystallised samples, beta-Ca2P2O7 and VP2O7 appeared as secondary phases. In the investigated temperature range, crystal growth rates 9 x 10 exp(-9)-2.14 x 10 exp(-6) m/s were determined. The temperature dependence of the crystal growth rate made it possible to calculate the activation energy, Ea = 407 plus or minus 30 kJ/mol, of crystallisation. The experimental data were compared with those estimated using a theoretical model of the crystal growth rate and good agreement was found. 25 refs.