Crystallization kinetics and mechanism of low-dielectric, low-temperature, cofirable CaO-B2O3-SiO2 glass-ceramics

The crystallization kinetics and mechanism of low-dielectric, low-temperature, cofirable CaO-B2O3-SiO2 glass-ceramics were investigated. Crystalline phases formed during firing included calcium silicates (CaSiO3, Ca3Si2O7, Ca2SiO4) and calcium berate (CaB2O4), with crystalline wollastonite (CaSiO3) the major phase. The crystallization kinetics of wollastonite followed an Avrami equation. The results of the present study showed an apparent activation energy of 200-260 kJ/mol, Combined with the results of reduced growth rate (growth rate x viscosity) and thermal analysis, the rate-controlling mechanism of crystallization appeared to be a two-dimensional surface nucleation growth. As the amount of crystalline wollastonite increased, the dielectric constant decreased, but the thermal expansion coefficient remained relatively unchanged.