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

CaO-B2O3-SiO2-Nb2O5 (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 Nb2O5, the combination of B-O and SiO would be destroyed, resulting in a decrease in the number of [BO31 and [SiO41 units. The results about DSC of glass powder showed that with the increase of Nb2O5 doping amount, the softening temperature (Tg) of glass, the initial temperature of the crystallization peak (Tc), the temperature corresponding to the endothermic peak intensity (Tp) of exothermic peaks and the activation energy values of the CaSiO3 and CaB2O4 crystal phase moved to high values, indicating that the crystallization of the CaSiO3 and CaB2O4 phase became difficult. The results of crystallization kinetics showed that the nucleation rate and crystallization rate decreased near Tc1 and Tc2, indicating that the crystal phase crystallization near Tc1 and Tc2 was inhibited. The critical cooling rate decreased with the addition of Nb2O5, indicating that the viscosity of the glass system increased. The XRD results of glassceramics showed that the main crystal phase of the sample changed from & alpha;-CaSiO3 to B-CaSiO3 and finally to CaNb2O6 with the addition of Nb2O5.The CBSN2 glass-ceramics sintered at 865 degrees C for 15 min had excellent dielectric properties: er = 6.42 and tan & delta; = 1.049 x 10-3 (1 MHz). The results indicated that CBSN glass-ceramics could be a potential LTCC substrate material.

Automated summary

CaO-B2O3-SiO2-Nb2O5 (CBSN) glass-ceramics were synthesized through melt water quenching and isothermal heat treatment. The addition of Nb2O5 disrupted the combination of B-O and SiO, reducing the number of [BO31 and [SiO41 units. Increasing Nb2O5 doping amount led to higher softening temperature (Tg), initial temperature of crystallization peak (Tc), temperature corresponding to the endothermic peak intensity (Tp), and activation energy values of CaSiO3 and CaB2O4 crystal phases, indicating hindered crystallization. The XRD results showed a phase transformation from α-CaSiO3 to B-CaSiO3 to CaNb2O6 with Nb2O5 addition. The CBSN2 glass-ceramics sintered at 865°C for 15 min exhibited excellent dielectric properties, indicating their potential as LTCC substrate material.