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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]

Cerium (Ce) and manganese (Mn) codoped Ba0.6Sr0.4TiO3(BST) films were prepared by improved sol-gel method and the effect of preheating on their dielectric properties was investigated. X-ray diffraction (XRD) reveals that the films grow principally along (110) orientations and show cubic perovskite structures. Preheating corresponds to smaller FWHMs, stronger crystallization and larger grain sizes, and preheating with codoping corresponds to the smallest FWHM, the strongest crystallization and the largest grain size. The prepared film can show tunability of 55.7%, dielectric loss of 0.0074∼0.0175 and approximately 75 FOM, meeting the needs of tunable microwave applications. [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 In the past four years, transition metal vanadates have received booming attention as anode materials for lithium ion batteries (LIBs) due to their outstanding specific capacities, decent cycling performance and superior rate properties. Among them, Co 3 V 2 O 8 is the most reported species. However the cobalt is expensive, thus the replacement of cobalt would be a favorable route. So far, mixed vanadates have been rarely reported because of the remarkable difficulty in fabrication, among which cobalt/nickel mixed vanadates are the most attractive. In this work, a facile and green hydrothermal method with organic linker has been developed, to achieve modulated cobalt/nickel mixtures. It was corroborated by the X-ray diffraction (XRD) patterns and cyclic voltammetry (CV) profiles that single phase of cubic Co 3 V 2 O 8 crystal structures were formed. The mixed vanadates demonstrated ultrahigh reversible capacity of over ∼1800 mAh/g at the current density of 0.2 A/g after ∼200 cycles and superb rate capability of ∼600 mAh/g at 4 A/g. The enhanced electrochemical performances of the higher-nickel-ratio indicated their considerable potential as high-capacity anode materials in LIBs. Graphical abstract Image 1 Highlights • Cobalt/nickel mixed vanadates were obtained via one-step and green hydrothermal process. • The mixed vanadates maintain the cubic crystal of Co 3 V 2 O 8 with nickel doping. • Higher concentration of doped nickel induced uniform nanoparticles smaller than 100 nm. • CoNi 2 V 2 O 8 delivered reversible capacity of 1800 mAh/g at 0.2 A/g and 600 mAh/g at 4 A/g. [ABSTRACT FROM AUTHOR]