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

The crystallization kinetics and mechanism of low-dielectric, low-temperatu re, cofirable CaO-B2O3-SiO2 glass-ceramics were investigated. Crystalline p hases formed during firing included calcium silicates (CaSiO3, Ca3Si2O7, Ca 2SiO4) and calcium berate (CaB2O4), with crystalline wollastonite (CaSiO3) the major phase. The crystallization kinetics of wollastonite followed an A vrami equation. The results of the present study showed an apparent activat ion energy of 200-260 kJ/mol, Combined with the results of reduced growth r ate (growth rate x viscosity) and thermal analysis, the rate-controlling me chanism of crystallization appeared to be a two-dimensional surface nucleat ion growth. As the amount of crystalline wollastonite increased, the dielec tric constant decreased, but the thermal expansion coefficient remained rel atively unchanged.