Microstructure and dielectric properties of Ca-Al-B-Si-O glass/Al₂O₃ composites with various alkali oxides contents

Abstract

The effects of alkali oxides (Na₂O and K₂O) addition on both the sintering behavior and dielectric properties of Ca-Al-B-Si-O glass/Al₂O₃ composites were investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results show that the increasing amount of alkali oxides in the glass causes the decrease of [SiO₄], which results in the decrease of the continuity of glass network, and leads to the decrease of the softening temperature T_f of the samples and the increasing trend of crystallization. And that deduces corresponding rise of densification, dielectric constant, dielectric loss of the low temperature co-fired ceramic (LTCC) materials and the decrease of its thermal conductivity. By contrast, the borosilicate glass/Al₂O₃ composites with 1.5% (mass fraction) alkali oxides sintered at 875 °C for 30 min exhibit better properties of a bulk density of 2.79 g/cm³, a porosity of 0.48%, a λ value of 2.28 W/(m·K), a ɛ_r value of 7.82 and a tan δ value of 9.1×10⁻⁴ (measured at 10 MHz).

Keywords

borosilicate glass / alkali oxides / Ca-Al-B-Si-O glass / Al₂O₃ / microstructure / thermal properties / dielectric properties

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