Crystallization Kinetics and Dielectric Properties of a Low‐Fire CaO–Al2O3–SiO2 Glass + Alumina System

Abstract

The crystallization kinetics and dielectric properties of a low‐dielectric, low‐temperature, cofirable ceramic system comprised of CaO–Al2O3–SiO2 (CAS) glass and alumina have been investigated. Crystalline phases including pseudowollastonite (CaSiO3), anorthite (CaAl2Si2O8) and cristobalite (SiO2) are formed during firing the pure CAS glass. The crystallization kinetics of both pseudowollastonite and cristobalite exhibit Avrami‐like behavior, and the results show apparent activation energies close to that of diffusion of alkali ions in the glass. With added alumina content greater than a critical value, the above crystalline phases are completely suppressed but more anorthite is formed. This result is attributed to the rapid dissolution kinetics of alumina into the CAS glass. As the degree of crystallization increases with firing time, the dielectric loss of the composite decreases significantly, however, with dielectric constant remaining relatively unchanged.