Preparation and properties of low temperature sintered CaO-B2O3-SiO2 microwave dielectric ceramics using the solid-state reaction

The LTCC CaO-B2O3-SiO2 (CBS) ceramics were synthesized via solid-state reaction process without any sintering aid. The effects of different sintering temperatures and B2O3 content on the microwave and mechanical properties were investigated. The results show that the best sintering temperature is around 950 °C and increasing amount of B2O3 promotes the crystallization of CaB2O4 enhancing the flexure strength of the CBS ceramics. However, the dielectric and mechanical properties deteriorated rapidly while the amount of B2O3 exceeded 25 wt.%. The sample with 20.5 wt.% B2O3 sintered at 950 °C had the best properties with ɛ r = 6.06; tanδ = 0.0015 (1 MHz) and a high flexure strength σ f > 180 MPa.