Crystallization behaviour in the glass system SiO2-Al2O3-P2O5-CaO-MgO-Nr(2)O

Crystallization of the multicomponent, mixed network glass having SiO2,Al2O3 and P2O5 as its framework formers, together willi CaO, MgO and Na2O as their modifiers,, as Elaborated Fourier transform infrared( FT-IR) spectroscopy was used to investigate the glass structure, while thermal properties were studied by means of differential scanning calorimetery(DSC), thermal mechanical analysis(TMA). X-ray diffraction(XRD), scanning electron microscopy( SEM), energy dispersive x-ray analysis(EDX) and optical microscopy, were utilized for the chractrization of the produced glass-ceramic Obtained results suggest that SiO, tetrahedra connected through AlO4-PO4 tetrahedral dimers constitute the network of the glass, causing an increase in its thermal stability, and consequently reducing its crystallization tendency. Homogenous bulk crystallization is achieved through a single-step heat-treatment schedule The depolymarization and reconstruction of the SiO2-AlPO4 network glass leading to its crystallization, depends on both, temperature and length of heat-treatment, and can be realized only when temperature and/or time are increased Fine crystallites of high cristobalite modification of AlPO4 is crystallizing, together with dense interconnected aggregates of Ca7Mg2P6O24 crystals, and somehow coarser flakelike crystals of whitlockite Ca-3(PO4)(2) The amount and morphology of the crystallized phases change as temperature and duration of heat-treatment are increased.