Aluminium influence on the crystallization and bioactivity of silico-phosphate glasses from NaCaPO4–SiO2 system

Silico-phosphate glasses of XCaPO4–SiO2 (X = Na+ and/or K+) system have been the subject of the presented investigations. One of the most important problems is to ensure proper biomaterial mechanical resistance. This can be achieved by introduction of proper additions, usually Al3+, into glass structure or/and partial glass devitrification. To design direct crystallization process properly it is necessary to know the texture and structure of the glassy precursor. Microscopic investigations have made it possible to find out that in all the glasses studied liquation takes place. A small addition of Al3+ influences homogeneity of the glass texture. It has been established (EDX investigations) that addition of aluminium dramatically changes the composition of the matrix and inclusions. Spectroscopic investigations (FTIR, NMR) have shown that both, the matrix and the inclusions exhibit domain composition whose structure is close to that of the corresponding crystalline phases. Domains can be considered as the specific ‘‘crystallization nuclei’’ which have a decisive impact on the process of directed glass crystallization. Based on DTA examinations it has been found out that crystallization of the glasses from XCaPO4–SiO2 system is a multistep process while the crystallization of glasses from XCaPO4–SiO2–AlPO4 system is a one step process.