Significant reduction of dielectric loss of Ba0.51Sr0.34TiO3 film modified by Y/Mn alternate doping and preheating

To achieve significant reduction of dielectric loss and enhancement of dielectric tunability for actual applications, a Ba_0.51Sr_0.34TiO₃ film modified by Y/Mn alternate doping (Y/Mn-BST_0.85) is prepared by an improved sol-gel method, where the film is composed of 12 layers, and odd number layers are preheated. For comparison, BST_0.85, Y-BST_0.85 and Mn-BST_0.85 films are also prepared. XRD shows four films are ABO₃ cubic perovskite structures. The BST_0.85 film shows the smallest lattice parameter and donor doping because rich Ti⁴⁺ ions enter into A sites to replace some Sr²⁺ and Ba²⁺ ions. Besides the donor doping, three doped BST_0.85 films exhibit slightly larger lattice parameters and acceptor doping because Y³⁺ or Mn²⁺ ions replace some Ti⁴⁺ ions at A sites. The Y/Mn-BST_0.85 film shows the largest lattice parameter and the strongest crystallinity because Y-BST_0.85 layer and Mn-BST_0.85 layer match well in lattice structure. Compared to stoichiometric films, four nonstoichiometric films show markedly decreased dielectric losses. The Y/Mn-BST_0.85 film exhibits the lowest dielectric loss with 0.45 ~ 0.54% under the conditions of ??40 to 40V and 100?kHz, and 0.43 ~ 2.29% under the conditions of 10?Hz ~ 1?GHz and 0?V, thus can satisfy actual applications including tunable microwave application at high frequencies. The related mechanisms are studied by measuring leakage current density, observing AFM and analyzing XPS besides analyzing the XRD patterns.