Effects of CaO Additions on the Structure and Dielectric Properties of Aluminoborosilicate Glasses

Abstract

Glasses with compositions xCaO-(60-x)SiO2-5MgO-15Al2O3-20B2O3 (x=0, 3, 6 and 9 mol %) were prepared by conventional melting method. Fourier-transform infrared spectroscopy (FTIR) indicated that the addition of CaO converted trigonal boron ([B) to tetrahedral boron ([B). The glass transition temperatures (Tg) were determined using a differential scanning calorimetry (DSC). Tg increased with increasing CaO content. Thus, the addition of CaO instead of SiO2 strengthened the glass network. The dielectric εr and loss tanδ were measured for the MgO-B2O3-Al2O3-SiO2 glass system in the frequency range 103-105 Hz. The decrease in εr and tanδ could be attributed to the increase in the rigidity of the glass network.