Preparation and properties of low temperature sintered CaO-B 2 O 3 -SiO 2 microwave dielectric ceramics using the solid-state reaction

The LTCC CaO-B 2 O 3 -SiO 2 (CBS) ceramics were synthesized via solid-state reaction process without any sintering aid. The effects of different sintering temperatures and B 2 O 3 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 B 2 O 3 promotes the crystallization of CaB 2 O 4 enhancing the flexure strength of the CBS ceramics. However, the dielectric and mechanical properties deteriorated rapidly while the amount of B 2 O 3 exceeded 25 wt.%. The sample with 20.5 wt.% B 2 O 3 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.