Dielectric and tunable characteristics of Ba0.4Sr0.6TiO3-BaWO4 composite ceramics for microwave applications

Phase compositions, microstructure and microwave dielectric properties, of BaWO₄ (BW)-Ba_0.4Sr_0.6TiO₃ (BST) composite ceramics, prepared by the traditional solid-state route, were systematically characterized. Meanwhile, mechanism of dielectric tunability of those materials was discussed. Dielectric properties of the BW-BST composites at a DC bias field near the phase transition temperature could be interpreted by using Johnson's phenomenological equation. The sample with x = 0.60 exhibited a tunability of 29.5%, a dielectric permittivity of 192 and a Q value of 231 (at 2.700 GHz), which make it a promising candidate for applications in electrically tunable microwave devices.