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

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)(6)O-2 oxyapatite (CLS) crystal for 20CaO-10Al(2)O(3)-60SiO(2)-10La(2)O(3) (mol%) glass and Ca2Nd8(SiO4)(6)O-2 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). (C) 1998 Chapman & Hall.