Study on sintering behaviors, microstructures, and dielectric properties of CaO-B2O3-SiO2/ZrSiO4 composites for LTCC applications

In this study, CaO-B2O3-SiO2 (CBS) glass-ceramics were prepared and compounded with different contents of ZrSiO4. The sintering behavior, phase composition, microstructure, dielectric properties, thermal properties, and mechanical properties of this CBS glass-ceramic composite ZrSiO4 ceramic system were investigated. The results show that CBS glass-ceramic can be sintered densely at 750 degrees C. However, the crystallinity is unexpectedly low and the dielectric properties are greatly damaged. Surprisingly, the addition of ZrSiO4 improved the dielectric constant of the composites and achieved a dielectric adjustable in the range of 6.0-7.8. When the composite was sintered at 830 degrees C for 15 min with 35% ZrSiO4 addition, the bulk density of the composite increased to 2.93 g/cm(3). The dielectric constant measured at a high frequency of 13 GHz was 6.93 and the dielectric loss of 1.66 x 10(-3). Accordingly, the addition of ZrSiO4 reduced the thermal expansion coefficient of the composite to 6.1 ppm/degrees C and increased the flexural strength of the composite to 248 MPa.