Glass constitution and crystallization characteristics of CaO-MgO-Al2O3-SiO2 glass-ceramic with P2O5 and F additions

To explore the effects of the additions Of P2O5 and fluorine on the glass formation region and crystallization in CaO-MgO-Al2O3-SiO2 glass, the base glasses were prepared by melt-quenching methods and the crystallizing behavior were investigated by using XRD and SEM techniques. The results indicate that the glass formation region is around (P2O5%+F%) <= 10%. In the sample with 4.0% in mass fraction of fluorine surface-dominated crystallization is suggested and the crystalline phases of anorthite (CaAl2Si2O8) as the major phase and wollastonite(CaSiO3) minor phase are precipitated. With the increase of fluorine contents, both surface and bulk crystallization are observed, forming the "volume" crystallization finally. The incorporation of P2O5 suppresses the surface crystallization, but inducing the appearance of phase- separation and bulk crystallization. When P2O5 and fluorine in combination are employed into the glasses, the bulk crystallization with fluoroapatite (Ca-5(PO4)(3)F) and anorthite as the main phases is obtained, in which, the increase Of P2O5 contents is beneficial to the forming of fluoroapatite, while the increase of fluorine content is favor to the precipitation of anorthite.