Crystallization, sintering, and dielectric characteristics of sol-gel synthesized CaO-B2O3-SiO2 glass-ceramics for LTCC applications

CaO-B 2 O 3 -SiO 2 (CBS) materials with varying Na 2 O concentrations were synthesized utilizing the sol-gel method. The structural evolution and crystallization characteristics of the glass, as well as the effects of Na 2 O amount on crystallization, firing densification, and dielectric performance of the sintered glass-ceramics, were studied. The study demonstrates that CBS glass can be successfully obtained through appropriate heat treatment of the CBS xerogel produced by the sol-gel process. The Na 2 O content significantly influences the rigidity of the glass structure and the composition of crystalline phases. An optimal Na 2 O content not only enhances firing densification but also improves the dielectric characteristics of this material. The specimen containing 1.5 wt% Na 2 O, fired at 875 °C, presents superior properties, including a density of 2.51 g/cm 3 , and a permittivity of 5.85, and a dielectric loss of 0.6 × 10 −3 (at 7 GHz). Moreover, the CBS glass-ceramic casting tape was fabricated via the tape casting route. The LTCC tape displays a dense particle-accumulated microstructure, achieving a tensile strength of 1.90 MPa and a surface roughness of 193 nm. This glass-ceramic also shows excellent temperature stability of dielectric properties and superior co-sintering compatibility with silver electrodes, demonstrating its extensive promise for LTCC applications.