Effects of BaO on crystallization, structure and dielectric properties of MgO–Al2O3–SiO2 glass–ceramics for LTCC applications

Abstract

Cordierite-based glass–ceramics for LTCC applications were prepared by traditional sintering method. And the effects of BaO addition on the crystallization, structure and dielectric properties were investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffractometer (XRD), dilatometer and impedance instrument. The DSC curves displayed that the glass transition temperature (Tg) slowly decreased with the BaO content increasing from 0 to 4 mol%. However, the onset of crystallization temperature (Tx) and crystallization peak temperature (Tc) showed the opposite trend. XRD analysis revealed that μ-cordierite was the major crystal phase for all the glass–ceramic samples, while α-cordierite precipitated as the minor crystal phase with BaO addition. As more BaO was added, the bulk density gradually increased, while the porosity decreased, indicating that BaO improved the sinterability of the glass samples. The dielectric constant showed minimum value with the addition of 2 mol% BaO, and the dielectric loss reached the minimum value when the content of BaO was 3 mol%. Wherein, after heated at 950 °C, glass–ceramics doped with 2 mol% BaO showed a dense structure, a relatively low dielectric constant (4.53), a low dielectric loss (2 × 10−3) at 1 MHz, and a proper CTE value (3.74 × 10–6/°C), which can be used to prepare LTCC materials.