The nucleation and crystallization kinetics of P2O5-B2O3-ZnO-Al2O3-TiO2 crystals in bulk glass in which these crystals were found to crystallize in the heating process of the glass, were studied by non-isothermal measurements using differential thermal analysis (DTA). A nucleation rate-temperature was determined by plotting either the reciprocal of the temperature corresponding to the crystallization peak maximum, 1/Tp, or the height of the crystallization peak, (Δ/T)p, as a function of nucleation temperature, Tn. The temperature where nucleation can occur for this glass ranges from 720 oC to 860 oC and the temperature for maximum nucleation is 820 ± 5 oC. The correct activation energy for crystallization, Ec, for this glass is the same for surface and/or bulk crystallization, and is 23 ± 15 kcal/mol. The analysis of the crystallization data with the Kissinger equation and the Marotta equation yields the correct value for Ec only crystal growth occurs on a fixed number of nuclei. The crystallization process of a sample heat treated at the temperature of the maximum nucleation rate was fitted to kinetic equations with an Avrami constant, n 3, 1 and a dimensionality of crystal growth, m 3, 1.

Keywords: Crystallization kinetics, Phosphate glass, Glass-ceramics, Surface nucleation