Crystallization behavior and properties of cordierite glass-ceramics with added boron oxide

The glass forming behavior and glass-ceramic formation of cordierite compositions in the MAS (MgO-Al2O3-SiO2) system with an added B2O3 content up to 3% were studied using glass samples prepared by melting the natural raw materials such as; talc, kaolin, alumina and boric acid as the source of MgO, SiO2, Al2O3 and B2O3. XRD (X-Ray powder diffraction) analysis revealed glass formation and after heat treatment at various temperatures, the crystallization of the cordierite phase was observed at 950 degrees C for a I h heat treatment. Some physical properties, such as the hardness and thermal expansion coefficient of glass and glass-ceramics were measured and compared in order to see the effect of crystallization. Surface crystallization was observed and the addition of boron oxide reduced the crystalline surface layer thicknesses. The main crystalline phase was cordierite and a small amount of forsterite was also observed in MAS glass-ceramics.