Structure and dielectric properties of zinc borate glass–ceramics modified by magnesium

The effects of magnesium substitution for zinc in zinc borate glass–ceramics [xMgO–(3 − x)ZnO–2B₂O₃ where x = 0, 0.1, 0.2, 0.3] prepared by conventional solid state on structure, crystallized temperature and dielectric properties were investigated. Fourier transform infrared spectrometer was used to investigate the variations of the glass structure. With increasing magnesium amount, the non-bridge oxygen amount increased, lowering the crystallized temperature. Surplus substitution leaded to the formation of boroxol rings and [MgO₄] groups in the glass structure, strengthening the glass structure. Thus, the crystallized temperature increased. Two main crystalline phases of α-Zn(BO₂)₂ and Zn₃B₂O₆ were found at the x level of 0 and 0.1 for the sintered samples, while Mg₃B₂O₆ appeared when the magnesium substitution achieved to 0.2 and 0.3. Further, the magnesium-substitution lowered the dielectric constant slightly due to its relatively low ionic polarizability and low magnesium content. When the 0.2 mol magnesium amounts was substituted for zinc, the specimens showed the optimal dielectric properties, with a dielectric constant of 6.7 and a dielectric loss of 1 × 10⁻³ after sintering at 640 °C for 30 min, which demonstrated a good potential for use in low temperature co-fired ceramic technology.