The 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 for the experiments. The crystallisation of bulk glass samples was performed tinder isothermal conditions at T = 650-820 degrees C. The surface crystallisation mechanism of studied glass with dendritic growth of the primary alpha-Ca2P2O7 phase was observed. In all crystallised samples, beta-Ca2P2O7 and VP2O7 appeared as the secondary phases. In the investigated temperature range, crystal growth rates 9 x 10(-9) - 2.14 x 10(-6) m/s were determined. The temperature dependence of the crystal growth rate makes possible to calculate activation energy E-a = 407 +/- 30 kJ/mol of crystallization. The experimental data were compared with those estimated by using a theoretical model of the crystal growth rate and good agreement between the results was found.