High performance low temperature sintered microwave dielectric ceramics prepared by solid-state reaction

In this work, a multi-step solid reaction method was introduced for preparing high performance low temperature sintered microwave dielectric ceramics. The CaO-SiO₂-B₂O₃ ternary system was investigated as a model material. Samples with different Ca/B/Si ratios were prepared. The phase composition, microstructure, and microwave dielectric properties were studied. The major crystalline phases of the studied compositions were CaSiO₃, Ca₂B₂O₅, and SiO₂. Bar-like crystallized phase were observed from the scanning electron microscopy images. Among these studied compositions, the 42%CaO-26%B₂O₃-32%SiO₂ component showed excellent microwave dielectric properties with a dielectric constant of 6.2 and Q·f value of 28200 (@13 GHz) at a sintering temperature of 980°C. The low dielectric loss attributes to the glass-free process and highly crystallized phase compositions. The sintering temperature could be reduced to 900°C by adding the BBAS material, and a dielectric constant of 5.9 and Q·f value of 11200 (@13 GHz) was obtained. The low temperature sintered ceramic is cofirable with Ag electrode.