Glass Formation in the MgO-B2O3-SiO2 System

The glass formation region in the MgO-B2O3-SiO2 system was determined by the conventional melt-quenching technique at 1450 degrees C. The homogeneous transparent glasses were obtained in the central part of the magnesium borosilicate system in the region between 40 and 60 mol% MgO content. The amorphous and crystalline phases were examined by means of X-ray diffraction, differential thermal analysis, and Fourier-transform infrared spectroscopy. According to differential thermal analysis data, the glass transition temperature ranges between 645 and 705 degrees C, and the glass crystallization temperature varies between 830 and 985 degrees C. The thermal stability of glasses decreases with the increase of MgO content. Some physical characteristics (thermal expansion coefficient, density, molar volume, and volume resistivity) of the glass samples were estimated as well. The thermal expansion coefficient, density, and molar volume of the MgO-B2O3-SiO2 glasses obtained in this study ranged from 5.4 to 7.6 ppm/degrees C, 2.53 to 2.70 g/cm(3), and 18.56 to 22.51 cm(3)/mol, respectively, depending on the glass composition. Fourier transform infrared spectroscopy results showed that the network of glasses consists mainly of BO3 and SiO4 structural units. These results may lead to the development of new materials with interesting applications in diverse fields because of their particular structural and physicochemical properties.