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Chemical solution deposition (CSD) of BaTiO3 (BT) or BT-based thin films relies on using a carboxylic acid and alcohol as the solvents for alkaline-earth carboxylate and transition-metal alkoxide, respectively; however, the esterification reaction of the solvents may lead to in-situ water formation and precipitation. To avoid such an uncontrolled reaction, we developed a route in which ethylene glycol (EG) is used as the solvent for Ba-acetate. The EG-based BT coating solutions are stable for at least a few months. The thermal decomposition of the BT xerogel obtained by drying the EG-based solutions depends on the choice of the solvent for the Ti-alkoxide as well: in the case of EG and 2-methoxyethanol solvents carbon residues are removed at only about 1100 °C, while in the case of ethanol it is concluded at about 700 °C. About 100 nm thick BT films derived from the EG-ethanol solution deposited on platinized silicon reveal dense, crack-free columnar microstructure. They exhibit local ferro- and piezoelectric properties. The macroscopic polarization-electric field loops were obtained up to a quite high electric field of about 2.4 MV/cm. The EG-ethanol based CSD route is a viable alternative to the established acetic acid–alcohol route for BT and BT-based films. [ABSTRACT FROM AUTHOR]

Ferroelectric properties of thin films can be enhanced by crystallographic texture. In this work, we report on how heat treatment of films can be designed to tailor the degree of preferential orientation in BaTiO3‐based thin films from aqueous chemical solution deposition. In situ synchrotron X‐ray diffraction in combination with Rietveld refinements was used to study the crystallization process of films from a single deposition and to give an in‐depth characterization of the crystallographic texture of the films. Transmission electron microscopy was employed to evaluate the microstructure and degree of preferred orientation in thicker films from multiple depositions. Texture was induced in the multilayer films by a repeated annealing process. Cube‐on‐cube growth was demonstrated to occur in both single and multi‐layered films provided the heating program was designed to give limited nucleation and growth below the threshold for where cube‐on‐cube growth is favoured, resulting in a very high degree of preferred orientation. The cube‐on‐cube grown films were relaxed with respect to the lattice unit cell mismatch between the film and the substrate, where the relaxation of stress depends on the film thickness. Texture and cube‐on‐cube growth were demonstrated on several types of single‐crystal oxide substrates. Calcium and zirconium substitution did not alter the crystallization process, but zirconium slowed down the texture formation kinetics. The ferroelectric response was strongest in the films with a high degree of preferred orientation. [ABSTRACT FROM AUTHOR]

Polycrystalline BaTiO3 thin films were grown solvothermaly on titanium foil by introducing barium hydroxide solution in a Teflon line and allowed to react with the foil during the autoclave process. Different molar concentration of Ba(OH)2 were investigated: 0.5, 1 and 2 mol·L−1 with three heating temperatures: 150, 175 and 200 °C. The films were characterized by XRD and revealed characteristic peaks of BTO with a slight preferential orientation along the [00l] directions. The SEM characterizations showed dense thin films with spherical grains. The relative permittivity is about 400 and dielectric losses below 0.05 in the frequency range 102 to 107 Hz. [ABSTRACT FROM AUTHOR]

Polycrystalline BaTiO3 thin films were grown solvothermaly on titanium foil by introducing barium hydroxide solution in a Teflon line and allowed to react with the foil during the autoclave process. Different molar concentration of Ba(OH)2 were investigated: 0.5, 1 and 2 mol·L−1 with three heating temperatures: 150, 175 and 200 °C. The films were characterized by XRD and revealed characteristic peaks of BTO with a slight preferential orientation along the [00l] directions. The SEM characterizations showed dense thin films with spherical grains. The relative permittivity is about 400 and dielectric losses below 0.05 in the frequency range 102 to 107 Hz. [ABSTRACT FROM AUTHOR]

Barium titanate (BaTiO3) thin films have been prepared using the spray pyrolysis method. The films were deposited onto a glass substrate at varying substrate temperature ranging from 250 to 350 °C with the interval of 50 °C. The structural, morphological, electrical and dielectric properties of the deposited films have been studied. The X-ray diffraction pattern confirmed the polycrystalline nature of the films with a cubic crystal structure. X-ray photoelectron spectroscopy (XPS) showed a good agreement of the thin films stoichiometry with BaTiO3. A presence of Ba, Ti and O in the BaTiO3 thin films was observed by energy dispersive X-ray analysis. The scanning electron microscopy (SEM) showed the heterogeneous distribution of cubical grains all over the substrate. The grain size decreased with an increase in substrate temperature. The dielectric constant and dielectric loss showed the dispersion behaviour as a function of frequency, measured in the frequency range of 20 Hz to 1 MHz. The AC conductivity (σac) measurement showed the linear nature of obtained films, which confirms conduction mechanism due to small polarons. Impedance spectroscopy has been used to study the electrical behaviour of BaTiO3 ferroelectric thin films. The ferroelectric hysteresis loop has been recorded at room temperature. [ABSTRACT FROM AUTHOR]

Ferroelectric BaTiO3thin films were successfully deposited on nickel foils by a chemical solution technique named polymer-assisted deposition. It is found that a second annealing in oxygen using a rapid thermal annealing furnace would strongly affect the electric properties of the as-prepared thin films. Dielectric and ferroelectric properties have been systematically studied. The correlation between the second annealing conditions and dielectric properties was established and discussed. Optimized second annealing condition was found. [ABSTRACT FROM PUBLISHER]

[Display omitted] • Surface composition of BaTiO 3 thin films is analyzed by XPS upon atmosphere exposure. • Over time down polarized surfaces are more active for oxidation and more hydrophilic. • High energy component in Ba 3d 5/2 spectra is related to barium peroxide (BaO 2). • O 2 annealing of BaTiO 3 films fosters oxidation of Ba sites and production of BaO 2. • Chemically assisted polarization switching from up to down state is observed. Dissociation and adsorption of water on ferroelectric oxide surfaces play important role in the processes of screening and switching dynamics of ferroelectric polarization, as well as in catalytic processes which can be additionally coupled with light, temperature or vibration stimuli. In this work, we present XPS study of ferroelectric BaTiO 3 thin films and determine the entanglement between surface chemistry, polarization direction and stability, by observing changes upon time exposure to environmental conditions, heating in O 2 atmosphere and irradiation in vacuum. We devote special attention to Ba 3d spectral region and identify two different oxidation states of O atoms in the compounds of Ba. While this second specie was generally attributed to Ba in surface compounds where it has different oxygen coordination than in the bulk, based on the XPS results of oxygen annealed thin films, we demonstrate that this so far neglected component, corresponds to barium peroxide (BaO 2) and identify it as important active specie for the study of screening mechanisms closely related with catalytic activity present in this ferroelectric material. Finally, we report on chemically assisted polarization switching in thin films induced by heating in vacuum or exposure to X-Ray radiation due to the formation of positive surface electric field created by oxygen or electron vacancies, respectively. [ABSTRACT FROM AUTHOR]

Abstract: In this work, electrophoretic deposition (EPD) technique was employed for fabricating the barium titanate (BaTiO3) films on the Si substrate modified with the ordered conducting polyaniline (PANI) layers. Firstly, surface polymerization of ordered conducting PANI layers on the Si substrate modified with the aniline-bearing silane self-assembled monolayer was performed by polymerization of aniline monomer in an acidic aqueous solution. Then, EPD of BaTiO3 films was fulfilled using the conducting PANI layers coated Si wafer as the cathode. The analytical results demonstrate that the crack-free, relatively dense and smooth BaTiO3 films have been accomplished on the PANI layers modified Si substrate with the appropriate suspension concentration and the deposited film thickness can be changed expediently by adjusting EPD process parameters. This method provides a potential route for fabricating ceramic films on the non-conductive Si or glass substrates using EPD technique. [Copyright &y& Elsevier]

Barium strontium titanate (BST) thin films have been intensively studied as a frequency and phase agile materials for the tunable microwave devices such as tunable filter, phase shifter and phased array antennas. The dielectric properties of BST thin films, including the dielectric constant, dielectric loss and tunability of capacitance are affected by many factors, such as Ba/Sr ratio, growth temperature, crystallographic orientation, grain size, defect chemistry, oxygen vacancies, strain and stress, and dopants. In this work, we report on the enhanced dielectric properties of (Ba 0.6 , Sr 0.4 )TiO 3 (BST) thin films for high-performance microwave tunable device applications. Epitaxial BST thin films were deposited on MgO substrates by the insertion of thin BaTiO 3 [BT] seed layers with intermediate lattice mismatch between the BST films and the MgO substrate using a pulsed laser ablation. Dielectric measurements were carried out using planar interdigitated (IDT) capacitor in ranges of RF/microwave frequency. IDT capacitor based on epitaxial BST film exhibited the large capacitance tunability of 77% at a frequency of 100 kHz and applied electric field of 80 kV/cm. CPW phase shifter showed the large phase tuning of 153° at 10 GHz and 40 V. These results indicate that it is a promising candidate for high-performance microwave phase shifters at room temperature. [ABSTRACT FROM AUTHOR]

Specific heat of polycrystalline BaTiO3 thin films on the fused quartz substrate was measured by ac-hot probe method. Phase transition temperature and excess entropy were determined as a function of film thicknesses and grain sizes. The variation of the latter was obtained in the limits 30-150 nm by changing of the temperature of the substrate during sputtering while thickness of films 20-1100 nm was controlled by the time of sputtering. It was found that the relation between the thickness and grain size is important for the size effects in polycrystalline films. [ABSTRACT FROM AUTHOR]