Effect of B2O3 on Structure and Properties of CaO–MgO–B2O3–Al2O3–SiO2 Glasses

xB 2 O 3 -(1 − x) (60SiO 2 –15Al 2 O 3 –15MgO–10CaO) glasses with various x around 5–30 mol% at the step of 5 mol% are prepared by the melting-quenching method at 1,450 °C for 3 h. The IR data indicate that replacing other components by B 2 O 3 levels up the amount of [BO 4 ] tetrahedron and boron-oxygen rings, forcing [AlO 4 ] tetrahedron to drop gradually. The glass transition temperature (T g ), crystallization temperature (T c ) and thermal stability (∆T) rise when B 2 O 3 is present in lower concentrations (≤20 mol%); accordingly the glass network enhances. However, further increase in concentration of B 2 O 3 (>20 mol%) reduces the T g , T c and ∆T. We utilize temperature-gradient furnace to measure the G6 glass, while the re-melt sample and crystallized phase are observed from polarizing microscope destroying microstructure. As B 2 O 3 content move up, falls in dielectric constant (ε r ) and loss (tanδ) can be associated with drop of cations polarizability as well as concentration, along with glass network rigidity ascending.