Synthesis and characterization of CBS glass/ceramic composites for LTCC application

Abstract

CBS (CaO–B 2O 3–SiO 2) glass/cordierite (Mg 2Al 4Si 5O 18) ceramic composites were prepared using standard ceramic process. Effects of cordierite on crystallization behavior of the CBS glass powder were investigated. Results showed that crystalline phases like pseudowollastonite (CaSiO 3) and quartz (SiO 2) were formed during the firing of glass alone. For the composites with ≥45 vol. % cordierite at 780–1200 °C, the above crystalline phases were completely prevented but new phase of anorthite (CaAl 2Si 2O 8) was formed. For all the composites, the intensity of peaks characterizing cordierite gradually decreases and that of characterizing anorthite synchronously enhances with increasing sintering temperature. Microstructural changes of all the samples with sintering temperature were in good agreement with the relative density and an optimum firing temperature for maximum densification existed for each glass/ceramic ratio. The thermal expansion coefficient (TEC) of the composites decreases with increase in cordierite ceramic volume percent. The TEC of all the composites was in the range of 2.2 × 10 −6 K −1 to 5.2 × 10 −6 K −1. The dielectric constant of the fabricated composites was between 5.2 and 6.2. The precipitation of anorthite has no bad effect on the dielectric constant and the TEC of the resulting composites because anorthite has low dielectric constant (6.2) and low thermal expansion coefficient (4.82 × 10 −6 K −1). The prepared glass/ceramic composites were well suited for LTCC application.