Determination of avrami parameters of hydroxyapatite and β-wollastonite in bioactive phosphor—Silica glasses

The properties of biologically active glasses in the system SiO₂?P₂O₅?MgO?CaO were studied. Crystalline hydroxyapatite (HA) and β-wollastonite (β-W) were used after heat treatment (1100°C). The influence of the glass particle size (0.071–2.5 mm) and of glass powder (d ₅₀=15.1 μm) on the behaviour of the products during differential thermal analysis was followed. These analyses indicated that the β-W probably originates from surface nucleation, and HA from bulk nucleation. The differentiation was confirmed by calculation of the Avrami parameters (n) with the Pi-loyan-Borchardt analytical method. For HA and β-W, the calculated values ofn were 2.96 and 1.91. The surface-nucleated glasses exhibited predominant bidimensional crystal growth.