Microstructure and dielectric properties of highly tunable Ba0.6Sr0.4TiO3/MgO/Al2O3/ZnO composite

Abstract The effect of co-doping ZnO, Al 2 O 3 and MgO on the microstructures and dielectric properties of Ba 0.6 Sr 0.4 TiO 3 ceramics prepared by the mixed-oxide route at 1400 °C was investigated. And a comparison criterion for the BST-based tunable ceramics was proposed. The results show that a cubic perovskite phase Ba 0.6 Sr 0.4 TiO 3 and a face-centered-cubic spinel phase Mg(Zn)Al 2 O 4 were observed in BST/MgO/Al 2 O 3 /ZnO (BMAZ) composite ceramics. When Zn 2+ content exceeds solid solubility limit in the BST, excess ZnO will react with Al 2 O 3 to produce ZnAl 2 O 4 phase. With the increase of ZnO, the paraelectric–ferroelectric phase transition points of BMAZ ceramics shift to the lower temperatures, and the maximum of dielectric constant increased first and then decreased. A higher tunability which amounts to 27.4% under 1.0 kV/mm biasing was obtained for BMAZ ceramics doped with 1.0 wt% ZnO.