Enhanced dielectric tunability and reduced dielectric loss in various donor–acceptor co-doped Ba_0.675Sr_0.325TiO₃ ceramics

In the present study, pure and donor–acceptor co-doped Ba_0.675Sr_0.325TiO₃ (BST) ceramics were prepared by the conventional solid-state reaction method. La was fixed as the donor dopant at A-site while Mn, Cr, and Fe were selected as the acceptor dopants at B-site. The effect of acceptor dopants on the microstructure and electrical properties of BST ceramics was investigated systematically from the view of different ionic radius and electronegativity. Enhanced dielectric tunability and reduced dielectric loss could be realized by co-doping, resulting in a significant improvement in the figure of merit (FOM). The optimum tunable properties were obtained in Mn–La co-doped ceramics with the dielectric tunability of 85.1%, the dielectric loss of 0.0018, and the FOM of 472. Such results could be attributed to the smaller ionic radius and weaker electronegativity of Mn. Compared to pure BST ceramics with the FOM of 40, co-doped BST ceramics exhibited great potential for tunable device applications. The breakdown strength (BDS) of BST ceramics was also studied in this work. Improved breakdown strength by co-doping took better stability for its applications under applied electric field.