Crystallization Kinetics and Heat Treatment Temperature on Microstructure of Na₂O-CaO-P₂O₅-TiO₂ Glass System

Abstract

Bioactive glass ceramics from Na2O-CaO-P2O5-TiO2 system have been fabricated by conventional melt quenching method. In order to change the fabricated glass to glass ceramic samples, a heat treatment technique was employed using temperatures ranging between 700 and 900°C for 2 h. Glass transition and crystallization temperature were analyzed via differential thermal analyzer (DTA). In addition, phase formation and microstructure of the glass-ceramics were also investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). From the crystallization kinetics, the crystallization rate constant (n) of the glass was found to be close to the value of 3, indicating the two-dimensional growth of crystals occurred in the glass ceramics. From the XRD results, the major crystalline phases were sodium titanium phosphate and calcium sodium phosphate along with titanium dioxide as the minor crystalline phases presented in high heat treatment temperatures (750-900°C) of the glass ceramics. SEM of the crystallized base glass Na2O-CaO-P2O5-TiO2 system, showed that crystallization of dendritic-like growths in the glass ceramics.