Glass-forming ability, sinter-crystallization behavior and microwave dielectric properties of MgO-B2O3-(Al2O3)-SiO2 glass-ceramics

The present work aims to survey sinterability, crystallization behavior and microwave dielectric characteristics of MgO-B2O3-SiO2 glass-ceramics in the presence of 1-10 weight ratios of Al2O3. It was shown that changing the base composition and addition of Al2O3 led to an increase in the glass-forming potential. Fully densified glass-ceramics were achieved by sintering below 950 degrees C from all selected compositions. During sintering, magnesium borate and magnesium silicate were formed in all specimens whilst cordierite was also crystallized in the specimens contained >5 weight ratios of Al2O3. Based on the FESEM observation, magnesium borate and magnesium silicate adopted a nanometric spherical morphology and cordierite had a platelet-like morphology. Due to the increased interface areas between crystalline phases and consequent intensified space charge polarization, addition of Al2O3 to the studied compositions did not affect dielectric properties, positively. However, the microwave dielectric characterization confirmed the suitability of the fabricated glass-ceramics as low-permittivity fully dense dielectric substrates. (C) 2016 Elsevier B.V. All rights reserved.