The effect of rare-earth oxides on the crystallization of CaO–Al2O3–SiO2 glasses

Abstract

CaO–Al₂O₃–SiO₂ –La₂O₃–Nd₂O₃ glass was prepared and their physical properties, such as density, glass transition temperature and crystallization temperature, were measured. The heat treatment of these glasses precipitated Ca₂La₈(SiO₄)₆O₂ oxyapatite (CLS) crystal for 20CaO–10Al₂O₃–60SiO₂–10La₂O₃ (mol%) glass and Ca₂Nd₈(SiO₄)₆O₂ oxyapatite (CNS) crystal was precipitated with Nd₂O₃ substitution. Crystallization of these glasses was observed at the surface and internally within the samples. The spherical and stick-like crystals were observed throughout the bulk of the glasses and the surface crystal layer of oxyapatite crystals were strongly oriented along the c-axis. The apparent activation energies of crystal growth were estimated as 360 kJ mol⁻¹.