Percolative property and microwave dielectric characterization of Ba0.4Sr0.6TiO3-Mg2TiO4 diphasic ceramics

Ba_0.4Sr_0.6TiO₃-Mg₂TiO₄ composite ceramics were fabricated via conventional solid state reaction process. Dielectric properties of the composites were investigated systematically. It was shown that their dielectric constants decreased monotonously from 1197 to 60 with the contents of increasing Mg₂TiO₄ from 0 to 70 wt%. Tunability had a slight change from 24.0% to 20.5% as the volume fraction of Mg₂TiO₄ was increased from 0 to 62 vol%. However, it decreased substantially from 20.5% to 13.4% above the threshold from 62 vol% to 71 vol%. Such an obvious change in tunability was well explained by connectivity levels of the binary composites. Q values of the composite ceramics were more than 200 (tg δ < 0.005) at microwave frequencies of less than 10 GHz. Dielectric dispersion was observed at about 22 GHz using interdigital capacitor (IDC) stucture.