Glass structure, crystallization kinetics and dielectric properties of CeO₂-added CaO–B₂O₃–SiO₂ glass system

This work investigated the effects of CeO₂ contents on structure, crystallization behavior and dielectric properties of CaO–B₂O₃–SiO₂ glass composition. The MAS-NMR results showed that B occurred as B^IIIa, B^IIIs and B^IV species and Si presented as Q², Q³ and Q⁴ units in the glasses. As the increase of CeO₂ content, the relative amounts of B^IV and B^IIIs unit decreased while the B^IIIa units increased, and the amounts of Q⁴ and Q² units increased while the Q³ unit decreased. With increasing CeO₂ content, the value of T_g decreased from 743 °C to 717 °C, the activation energy for CaSiO₃ first increased and then decreased. For glass–ceramics samples sintered at 825 °C, all samples had the crystalline phases of CaSiO₃, CaB₂O₄, Ca₂SiO₄. In addition, the samples with CeO₂ content more than 1 mol% had CeO_1.695 phase, which changed to be the main crystalline phase when the content of CeO₂ increased up to 10 mol%. The ε_r of the glass–ceramic samples with CeO₂ content x ≤ 6 showed an ascend trend in total, and decreased sharply to 4.1 for the sample with x = 10. However, the dielectric loss tan δ would not change significantly with the increasing of CeO₂ content. The samples with 1 mol% CeO₂ sintered at 825 °C owned ε_r of 5.4, tan δ of 0.9 × 10^− 3, and CTE of 7.8 × 10^− 6/K. The results indicated that CaO–B₂O₃–SiO₂ with CeO₂ glass–ceramics could be a potential LTCC substrate material.