Direct crystallization of silicate-phosphate glasses of NaCaPO 4-SiO2 system

Abstract

The subject of the study was silicate-phosphate glasses of NaCaPO 4-SiO2 system which are precursors of glass-crystalline materials. Glass-crystalline materials of NaCaPO4-SiO2 system obtained via crystallization of glasses belong to a group of the so-called bioactive materials. In order to obtain glass-crystalline materials with pre-established parameters, it is necessary to conduct crystallization of glasses at specific conditions. In order to design direct crystallization process properly, it is necessary to know the structure and microstructure of the glassy precursor. Microscopic investigation showed that liquation takes place in all the studied glasses. Based on DSC examinations, it has been found out that crystallization of the glasses of NaCaPO4-SiO2 system is a multistep process. The presence of several clearly separated exothermic peaks in DSC curves of investigated glasses makes it possible to crystallize only the separated phase with the matrix remaining amorphous or vice versa. Conducted detailed X-ray and spectroscopic studies of the materials obtained by heating in a gradient furnace (in the temperature specified on the basis of DSC) showed that separated phase and matrix crystallizes separately. Therefore, bioactive glass-crystalline materials can be obtained due to the existence of the phase separation phenomenon and pre-established sizes of the crystalline phase. © 2013 The Author(s).