The Influence of P2O5 on the Structure, Crystallization, and Bioactivity of Silicate-Based Bioactive Glasses and Glass-Ceramics

This study investigates the effects of P2O5 addition on the structural, thermal, and bioactive properties of silicate-based bioactive glasses and glass-ceramics. Four glass compositions (G0, G1, G2, G3) with varying P2O5 content (0.0, 2.5, 5.0, and 7.5 wt%) were prepared using the melt-quenching method. The samples were characterized using differential thermal analysis, X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and in vitro bioactivity tests in simulated body fluid. Results indicate that P2O5 addition lowers the glass transition temperature, promotes phase separation, and enhances the crystallization of fluoroapatite while reducing the formation of fluorophlogopite. In vitro tests revealed that P2O5 accelerates the formation of a hydroxycarbonate apatite layer on the glass surface, indicating improved bioactivity. However, in glass-ceramics, P2O5 delays ion release and HCA formation due to the stabilization of the residual glass phase. These findings suggest that P2O5 plays a critical role in tailoring the bioactivity and mechanical properties of bioactive glasses and glass-ceramics for biomedical applications.