Narrow Results

Titanium thin films were deposited by DC magnetron sputtering. The glancing angle deposition (GLAD) method was implemented to prepare two series of titanium films: perpendicular and oriented columnar structures. The first series was obtained with a conventional incident angle α of the sputtered particles (α = 0°), whereas the second one used a grazing incident angle α = 85°. Afterwards, the films were annealed in air using six cycles of temperature ranging from 293 K to 773 K. DC electrical conductivity was measured during the annealing treatment. Films deposited by conventional sputtering (α = 0°) kept a typical metallic-like behavior versus temperature (σ_{300 K} = 2.0 × 10⁶ S m^-1 and TCR_{293 K} = 1.52 × 10^-3 K^-1), whereas those sputtered with α = 85° showed a gradual transition from metal to dielectric. Such a transition was mainly attributed to the high porous structure, which favors the oxidation of titanium films to tend to the TiO₂ compound.

Based on the percolation threshold theory of conductive-dielectric composites, the dielectric constant can be improved more by adding a certain mass fraction of conductive particle into polymer matrix. However, the dielectric loss increases with the increasing mass fraction of conductive particle. In this paper, conductive Polyaniline (PANI) with different particle sizes is utilized to illustrate that reducing particle size can improve the dielectric properties. The dielectric constant is increased from 319 to 540, and dielectric loss is decreased from 2.34 to 0.85 when PANI with smaller particle size is used. Moreover, PANI coated with an insulating surfactant layer can further improve the dielectric properties, the experimental results show that the dielectric constant of the composite could be more than 1000, while the dielectric loss is 0.35 at 1KHz.

Flexible Nd-doped BaTiO₃@Al₂O₃/polyvinylidene fluoride (PVDF) composites have been successfully developed. With the reaction temperature of 70^∘C, Nd-doped BaTiO₃@Al₂O₃ particles display uniform core–shell structures and disperse well in the PVDF matrix. Due to the benign dielectric properties of Nd-doped BaTiO₃ and great suppression of the Al₂O₃ coating on the leakage current and dielectric loss, the Nd-doped BaTiO₃@Al₂O₃/PVDF composites with different Nd-doped BaTiO₃@Al₂O₃ filling ratios (0–4vol.%) exhibit relatively good dielectric and energy storage performance. Among them, the maximum discharged energy density of 8.6J/cm³ was achieved in the composite with 1vol.% Nd-doped BaTiO₃@Al₂O₃ loading.

The film structures on the base of soft and crystalline ferroelectrics (poly(vinylidene fluoride - trifluoroethylene) copolymer and deuterated triglycine sulfate) were produced. The volume content of the DTGS microcrystal particles embedded in the polymer matrix of the composite films was up to 10%. It was found crystalline phase changes in the polymer matrix at the DTGS inclusions presence. The DTGS crystal particles increased dielectric permittivity and electrical conductivity of the composite films. The temperature dependences of the dielectric permittivity indicated increasing the phase transition temperature of polymer matrix at the DTGS inclusions growth.

Effects of thermal misfit strains on dielectric features for sandwich structural barium strontium titanate (BST) thin films on metal plates were investigated via a modified thermodynamic model. When TEC of substrates is closer to that of BST, larger permittivity and tunability can be received. The tendency of permittivities and tunabilities of such films as a function of TEC of substrates agrees with that of single compositional BST films and compositionally graded BST multilayer films. The highest tunability reaches 60% at the biasing field of 300 kV/cm when the films are onto Ti metal. Moreover, Ba${}_{0.6}$Sr${}_{0.4}$TiO₃/Ba${}_x$Sr${{}_{1-}}_x$TiO₃/Ba${}_{0.6}$Sr${}_{0.4}$TiO₃ structure can obtain higher tunability than Ba${}_x$Sr${{}_{1-}}_x$TiO₃/Ba${}_{0.6}$Sr${}_{0.4}$TiO₃/Ba${}_x$Sr${{}_{1-}}_x$TiO₃ structure, while Ba${}_x$Sr${{}_{1-}}_x$TiO₃/Ba${}_{0.6}$Sr${}_{0.4}$TiO₃/Ba${}_x$Sr${{}_{1-}}_x$TiO₃ films show better compatible composition range for relatively larger tunability. Dielectric properties of sandwich-like BST films in some references can also be analyzed based on our calculated results.

Misfit strain, lattice parameter, polarization, permittivity, and tunability of Ba${}_{0.6}$Sr${}_{0.4}$TiO₃ thin films onto Ba${}_x$Sr_1−xTiO₃-buffered stainless steel (SS) substrates are computed via a modified phenomenological model. When the Ba/Sr ratio of Ba${}_x$Sr_1−xTiO₃ buffer layer grows, the permittivity and tunability first increase and then decrease with the maximum at $x$ = 0.75. The highest tunability of such films prepared by the sol-gel technique can reach 32.5% at the electric field of 320 kV/cm when $x$ = 0.8. The strains are qualitatively analyzed through combining XRD, Raman, and theoretical calculation. The computed data are generally supported by experimental lattice parameters, permittivities, and tunabilities, which show that polycrystalline BST thin films with smaller compressive strain obtain higher dielectric response, and that inserting buffer layer could regulate the strains and dielectric properties of BST thin films.