Lead-free (Ba,Sr)TiO₃-based ceramics with superior tunable properties by the semi-solution method

High-performance dielectric tunable materials with both high dielectric tunability and low dielectric loss are in urgent need of new-generation electronic tunable devices. In the present study, a new system (Ba_0.675Sr_0.325)_1-xLa_xTi_1-xMn_xO₃ (x = 0.25%, 0.5%, 0.75%, 1.0%) was designed. The acceptor dopant Mn was added to lower dielectric loss while the donor dopant La was introduced to enhance dielectric tunability. The samples were prepared by the conventional solid-state reaction method and the semi-solution method. Experimental results showed that the morphology of the ceramics was optimized by further improving the processing procedure. Dense microstructure, homogeneous grains, and uniform dopant distribution could be achieved successfully by the semi-solution method. Meanwhile, significant enhancement in the tunable properties was realized owing to the improved microstructure mentioned above. The optimum tunable properties occurred in the samples prepared by the semi-solution method at x = 0.75% with high dielectric tunability of 85.0%, low dielectric loss of 0.0011, and an excellent figure of merit (FOM) of 773. The tunable properties of BST ceramics were even superior to that of the lead-based materials with a FOM of around 700. All the results suggested that the semi-solution method rendered BST ceramics become more promising for the applications of tunable devices.