Enhanced dielectric tunability and reduced dielectric loss in the La/Fe co-doped Ba0.65Sr0.35TiO3 ceramics

• Achieve the high dielectric tunability and the reduced dielectric loss by La/Fe co-doping in Ba 0.65 Sr 0.35 TiO 3 ceramics. • Improve the figure of merit to 197 which is nearly 5 time compared to the pure Ba 0.65 Sr 0.35 TiO 3 ceramics. • Enhance the breakdown strength by 86% due to the reduced grain size and dense microstructure. In the present study, (Ba 0.65 Sr 0.35 ) 1−x La x Ti 1−x Fe x O 3 (x = 0, 0.0025, 0.005, 0.01) ceramics were designed and prepared by the conventional solid-state reaction method. The microstructures and electrical properties of La/Fe co-doped Ba 0.65 Sr 0.35 TiO 3 ceramics were investigated. Enhanced dielectric tunability and reduced dielectric loss were achieved in this system. The acceptor dopant Fe 3+ was used to lower dielectric loss while the donor dopant La 3+ was added to improve dielectric tunability. The optimum tunable properties took place at x = 0.0025 with the dielectric tunability = 78.8% and the dielectric loss = 0.0040. The figure of merit (FOM) was improved to 197, about five times that of pure BST. The breakdown strength (BDS) enhanced from 59.9 kV/cm to 111.4 kV/cm by La 3+ and Fe 3+ dopant, which promoted the stability of BST ceramics under high applied electric field. In conclusion, excellent tunable properties and improved breakdown strength made it possible for the La/Fe co-doped BST ceramics to be promising for tunable microwave applications.