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To achieve significant reduction of dielectric loss and enhancement of dielectric tunability for actual applications, a Ba 0.51 Sr 0.34 TiO 3 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 ABO 3 cubic perovskite structures. The BST 0.85 film shows the smallest lattice parameter and donor doping because rich Ti 4+ ions enter into A sites to replace some Sr 2+ and Ba 2+ ions. Besides the donor doping, three doped BST 0.85 films exhibit slightly larger lattice parameters and acceptor doping because Y 3+ or Mn 2+ ions replace some Ti 4+ 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. [ABSTRACT FROM AUTHOR]

Abstract: Mn and Y alternately doped Ba0.6Sr0.4TiO3 (Mn/YBST) films were prepared by improved sol–gel method on Pt/Ti/SiO2/Si substrates. The effect of different doped concentrations (0.5%, 1.0%, 1.5%, 2.0% and 2.5%) on crystallization and dielectric properties of BST films was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and HP4294A. All films grow along (110) orientation, possessed dense nodular microstructure, exhibited decreased grain size and improved morphologies with smaller average roughness. As a result, the doping behavior changes from donor doping to acceptor doping and again to donor doping and the dielectric constants and the dielectric losses tend to decrease with increasing doped concentration. 1.5% corresponds to the optimized dielectric properties with the dielectric losses of about 0.007 and the figure of merit (FOM) of 38.83 at 100kHz. Also, the related mechanisms and the dielectric properties at microwave frequencies are discussed. [Copyright &y& Elsevier]

By adjusting film thickness, smooth and dense Mn and Y alternately doped Ba0.6Sr0.4TiO3(Mn/Y-BST) films have been designed and prepared by improved sol-gel method, and the structure and dielectric properties of the films have been studied. X-ray diffraction (XRD) reveals that all films grow along (110) orientation, doped Mn2+ions or Y3+ions show acceptor doping, and thicker film shows stronger crystallization. Atomic force microscope (AFM) shows the films are relatively smooth without obvious cracks or pinholes. Scanning electronic microscope (SEM) indicates that from substrate to surface the films show nodular microstructures to columnar ones without obvious interface among nodular microstructure layers. Compared to pure BST film or Mn or Y doped BST films, all alternately doped films show markedly improved structures and dielectric properties, which is strongly dependent on film thickness. 6-layer Mn/Y-BST film shows best structure and combination of dielectric properties with dielectric loss of 1.18%, tunability of 38% and figure of merit (FOM) of 32.2 at 100 kHz. [ABSTRACT FROM AUTHOR]

Abstract: Mn and Y alternately doped Ba0.6Sr0.4TiO3 film, denoted as Mn/Y-BST film, has been designed and prepared by improved sol–gel method, and the structure and dielectric properties of the film have been studied. Y or Mn doped BST film is also studied. X-ray diffraction reveals that all films grow along (110) orientation and show polycrystalline cubic perovskite structures, and Y3+ and Mn2+ ions enter into B-sites of ABO3 perovskite structure and substitute Ti4+ ions. The Mn/Y-BST film reveals better crystallization with larger crystal grain size. Atomic force microscopy and scanning electron microscopy confirm that the Mn/Y-BST film exhibits better crystallization. X-ray photoelectron spectroscopy shows that the Mn/Y-BST film presents less surface non-perovskite structure. Accordingly, the Mn/Y-BST film exhibits significantly nonlinear improvement in combination of dielectric properties. These results indicate that Mn/Y alternate doping is a novel route to excellent BST films for tunable microwave applications. [Copyright &y& Elsevier]

Abstract: Ba0.6Sr0.4TiO3 thin films were deposited on Pt/SiO2/Si substrate by radio frequency magnetron sputtering. High-resolution transmission electron microscopy (HRTEM) observation shows that there is a transition layer at BST/Pt interface, and the layer is about 7–8nm thickness. It is found that the transition layer was diminished to about 2–3nm thickness by reducing the initial RF sputtering power. X-ray photoelectron spectroscopy (XPS) depth profiles show that high Ti atomic concentration results in a thick interfacial transition layer. Moreover, the symmetry ν of ɛ r–V curve of BST thin film is enhanced from 52.37 to 95.98%. Meanwhile, the tunability, difference of negative and positive remanent polarization (P r), and that of coercive field (E C) are remarkably improved. [Copyright &y& Elsevier]