Dielectric tunability and microwave properties of Ba0.5Sr0.5TiO3-BaMg6Ti6O19 composite ceramics for tunable microwave device applications

Ba0.5Sr0.5TiO3-BaMg6Ti6O19 microwave composite ceramics with low dielectric constant and relatively high tunability were fabricated via the solid-state reaction method. The microstructures and microwave dielectric properties of the composite ceramics have been investigated. BaMg6Ti6O19 and Ba0.5Sr0.5TiO3 can be friendly coexistent in the composite material system without obvious chemical reactions. With increasing content of BaMg6Ti6O19 from 10 wt.% to 60 wt.%, the dielectric anomalous peaks of ferroelectric-paraelectric phase transition for the composite ceramics are suppressed and broadened. The dielectric constant can be effectively tailored from 2035 to 129. For composite ceramics with 60 wt.% content of BaMg6Ti6O19, the dielectric loss still keeps around 0.002 and the tunability is 13.4% measured at a dc-applied electric field of 30 kV/cm. The Q value of composite ceramics with 20 wt.% content BaMg6Ti6O19 is 367 and the dielectric constant is cut down to 665 at the microwave band of 1.579 GHz.