Crystallization mechanism and properties of CaO-B2O3-SiO2-Nb2O5 (CBSN) glass-ceramics

CaO-B ₂O ₃-SiO ₂Nb ₂O ₅ (CBSN) glass-ceramics were produced by melt water quenching and isothermal heat treatment in this paper. The FTIR results showed that with the addition of Nb ₂O ₅, the combination of B-O and Si-O would be destroyed, resulting in a decrease in the number of [BO ₃] and [SiO ₄] units. The results about DSC of glass powder showed that with the increase of Nb ₂O ₅ doping amount, the softening temperature ( T_g) of glass, the initial temperature of the crystallization peak ( T_c), the temperature corresponding to the endothermic peak intensity ( T_p) of exothermic peaks and the activation energy values of the CaSiO ₃ and CaB ₂O ₄ crystal phase moved to high values, indicating that the crystallization of the CaSiO ₃ and CaB ₂O ₄ phase became difficult. The results of crystallization kinetics showed that the nucleation rate and crystallization rate decreased near T _c1 and T _c2, indicating that the crystal phase crystallization near T _c1 and T _c2 was inhibited. The critical cooling rate decreased with the addition of Nb ₂O ₅, indicating that the viscosity of the glass system increased. The XRD results of glass-ceramics showed that the main crystal phase of the sample changed from α-CaSiO ₃ to β-CaSiO ₃ and finally to CaNb ₂O ₆ with the addition of Nb ₂O ₅.The CBSN ₂ glass-ceramics sintered at 865 °C for 15 min had excellent dielectric properties: ε _r = 6.42 and tanδ = 1.049 × 10 ⁻³ (1 MHz). The results indicated that CBSN glass-ceramics could be a potential LTCC substrate material.