Investigating the Crystallization Process of Boron-Bearing Silicate-Phosphate Glasses by Thermal and Spectroscopic...

Glasses and devitrificates from the SiO₂-B₂O₃-P₂O₅-K₂O-CaO-MgO system with constant contents of SiO₂ and P₂O₅ network formers, modified by the addition of B₂O₃, were analyzed. All materials were synthesized by the traditional melt-quenching technique. The glass stability (GS) parameters (K_rg, ∆T, K_W, K_H) were determined. The effect of the addition of B₂O₃ on the GS, liquation phenomenon, crystallization process, and the type of crystallizing phases were examined using SEM-EDS, DSC, XRD, and Raman spectroscopy imaging methods. It was observed that the addition of B₂O₃ increased the tendency of the glass to crystallize. Both phosphates (e.g., Ca₉MgK(PO₄)₇, Mg₃Ca₃(PO₄)₄), and silicates (e.g., K₂Mg₅(Si₁₂O₃₀), CaMg(Si₂O₆), MgSiO₃) crystallized in the studied system. The Raman spectrum for the orthophosphate Mg₃Ca₃(PO₄)₄ stanfieldite type was obtained. Boron ions were introduced into the structures of crystalline compounds at high crystallization temperatures. The type of crystallizing phases was found to be related to the phenomenon of liquation, and the order of their occurrence was dependent on the Gibbs free enthalpy.