BaTiO3 Composite Films Research Articles

Effect of BaTiO3 on the sensing properties of PVDF composite-based capacitive humidity sensors

Capacitive humidity sensors consisting of materials such as polymers, ceramics, and piezoelectrics are widely used to monitor relative humidity levels. The effect of barium titanate (BaTiO3) nanoparticles on the humidity sensing properties, dielectric response, thermal stability, and hydrophilicity of the polyvinylidene fluoride (PVDF)-BaTiO3 composite films is investigated. Hydrophilicity and surface morphology of the PVDF-BaTiO3 composite films are modified for the development of a good humidity sensor. The nanocomposite solutions are prepared by mixing an optimized concentration (2.5 wt%) of PVDF with different concentrations (0.5, 1, and 2 wt%) of BaTiO3 nanoparticles. X-ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy, and contact angle measurements are used to characterize the structure, morphology, thermal stability, and hydrophilicity of the spin-coated sensing films. The dielectric study of PVDF-BaTiO3 composite film shows that as the concentration of BaTiO3 particles increase, the dielectric constant of the composite films increases as well. PVDF-BaTiO3 (2.5 wt%-1 wt%) based capacitive sensors show stable capacitive response and low hysteresis as compared to the other concentrations of the PVDF-BaTiO3 composites. The maximum hysteresis of the capacitive PVDF-BaTiO3 (2.5 wt%- 1 wt%) humidity sensor is found to be ~2.5%. The response and recovery times of the PVDF-BaTiO3 (2.5 wt%-1 wt%) based capacitive sensors are determined as 40 s and 25 s, respectively, which are significantly lower than those reported for the other PVDF composite based sensors.

Flexible /PET/batio3/ layer–layer composite film with enhanced dielectric properties fabricated by highly loaded /batio3/ coating with acrylic resin as binder

ABSTRACTFlexible layer–layer poly(ethylene phthalate) (PET)/BaTiO3 composite films with enhanced dielectric permittivity were fabricated by spin coating method, consisting of PET substrate film layer and modified BaTiO3/acrylic resin hybrid coating layer. The thickness of coating layer was less than 3 μm (about 2% of PET film thickness), and therefore, the PET/barium titanate (BT) composite films remained flexible even at high volume fraction of BaTiO3 fillers. The volume contents of BaTiO3 were varied from 0 to 80%, and the solid contents of BaTiO3/acrylic resin were in the range of 51.8–72.9%. Scanning electron microscopy showed strong interaction of finely dispersed BaTiO3 particles with acrylic resin. Morphological profile also displayed uniform coating layer of modified BaTiO3/acrylic resin and its strong adhesion with PET film. The dielectric constant of the PET/BaTiO3 composite films increased by about 26% at 60 vol % BaTiO3 loading when compared with the pristine PET film, whereas the dielectric loss decreased slightly. In addition, PET‐grafted poly(hydroxylethyl methacrylate) brushes were used as substrate to introduce covalent bonding with the coating layer. Further enhancement of dielectric constant and reduction of dielectric loss were realized when compared with the composite films with bare PET substrate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42508.

Preparation and electric field driven magnetoelectric effect for multiferroic La2/3Sr1/3MnO3/BaTiO3 composite films

Using pulsed laser deposition, multiferroic La2/3Sr1/3MnO3(LSMO)/BaTiO3(BTO) composite films are deposited on LaAlO3 (LAO)(001) substrate. X-ray diffraction results show that LSMO and BTO films exhibit only (001) orientation. Film smoothness is verified by their low root-mean-square surface roughness values as 1.4 nm from atomic force microscope study. The magnetic and the electric properties of these composite films are investigated. Furthermore, the variations of resistivity and metal-insulator transition temperature TMI of LSMO, induced by the external electric field, are studied. The resisitivity is reduced while the TMI is enhanced for hole accumulation state which is induced by negative electric field across BTO layer. In contrast, the resistivity is enhanced while the TMI is reduced for hole depletion state, which shows coupling between magnetic and electric order parameters, i.e., there is a magnetoelectric effect induced by electric field.

Optical properties of carbon nanotubes and BaTiO 3 composite thin films

Multiwalled carbon nanotubes and BaTiO3 composite films have been prepared by pulsed-laser deposition technique at room temperature and high temperature of 600°C, separately. The structures of the composite films are investigated by using scanning electron microscopy and x-ray diffraction. The optical behaviours of the samples produced at different temperatures are compared with Raman spectroscopy, and UV-visible absorption. And the observation by Z-scan technique reveals that the composite films have a larger optical nonlinearity, and the samples prepared at high temperatures have better transmittance and opposite sign imaginary part of optical third-order nonlinearity.

Peaks separation of the nonlinear refraction and nonlinear absorption induced by external electric field

To investigate the relation between the nonlinear susceptibility and the wavelength, Ag:BaTiO3 composite films were synthesized on MgO(100) substrates under different external electric fields using pulsed laser deposition. The nonlinear optical properties of the films were measured by z-scan in the wavelength of 355–650nm. It is found that with increasing the electric field, the peak of the nonlinear refraction index shifts to longer wavelength (redshift) and is separated from the peak of the nonlinear absorption. With the separation, the values of ∣Reχ(3)∕Imχ(3)∣ can be enhanced obviously.

Optical properties of laser ablated Ag:BaTiO3 composite films

Nanocomposite films composed of Ag particles embedded in BaTiO3 matrix were grown on MgO(100) substrates by pulsed laser deposition. The structures of the films were determined by X-ray diffraction. The size and shape of the Ag particles were observed by transmission electron microscopy. The X-ray photoelectron spectroscopy results showed that Ag is in the metallic state. The optical absorption properties were measured from 300 to 800nm, and the absorption peaks due to the surface plasmon resonance of Ag particles were observed. With increasing annealing temperature and Ag concentration, the peak absorption increased and shifted to longer wavelength (red-shift).

Enhancement of optical nonlinearity in Ag:BaTiO3 composite films by applying an electric field during growth

We prepared the Ag:BaTiO3 composite films by pulsed-laser deposition technique. The films were grown on MgO (100) substrates under a nitrogen pressure of 10.0 Pa at 600°C, and a parallel electric field was applied on the substrate during growth. The chemical natures of Ag in the films were measured by x-ray photoelectron spectroscopy. The linear optical properties of the films were studied in the wavelength range of 330 to 700 nm. The third-order nonlinear optical susceptibilities of the films were determined by z-scan method at the wavelength of 532 nm with a laser duration of 10 ns. The figure of merit (FOM) was ∼1 order of magnitude larger than that of the films that were grown without an electric field and reached 1.62×10^−10 esu cm. Our experimental results have demonstrated that an external electrical field can induce the metal-particle orientation in order and therefore enhances the FOM of the metal-dielectric composite films.

Nonlinear refraction and saturable absorption in Au:BaTiO3 composite films.

Composite thin films Au:BaTiO3, comprising nanometer-sized gold particles embedded in barium titanate matrices, were synthesized on MgO (100) substrates with the pulsed laser deposition technique. The nanostructure of the films and the size distributions of the Au particles were analyzed by high-resolution transmission electron microscopy. Crystal lattice fringes from the Au nanocrystals and the BaTiO3 matrices were observed. The nonlinear optical properties of the Au:BaTiO3 films were measured with the z-scan method at a wavelength of 532 nm, which was closed to the surface plasmon resonance of nanoscale Au particles. The features of the closed-aperture z-scan transmittance curves were affected by the ratio, which increased greatly at a high metal concentration, of the imaginary part to the real part of the third-order nonlinear susceptibility chi(3).

Resonant absorption quenching and enhancement of optical nonlinearity in Au:BaTiO3 composite films by adding Fe nanoclusters

We present an approach to enhance the figure of merit χ(3)/α (with χ(3) being the third-order nonlinear susceptibility and α the optical absorption coefficient) in metal-dielectric composites. Nanocomposite thin films containing metal nanoclusters were obtained by embedding gold, or gold+iron in BaTiO3 matrices using the pulsed laser deposition technique. In the optical absorption spectra, the Au:BaTiO3 films showed a strong absorption peak around 562 nm due to surface plasmon resonance of Au particles. However, when a small amount of Fe was added, the resonant absorption was quenched, and χ(3) was enhanced so that χ(3)/α was significantly increased. Our study suggests a method by which to design optical nonlinear materials with large figure of merits for practical application.

The application of nanocrystalline BaTiO 3-composite films as CO 2-sensing layers

A new generation of solid state sensors based on nanocrystalline BaTiO 3 films containing various semiconducting oxides has been developed. The sensors were fabricated from BaTiO 3-based nanopowder mixtures using thick film technology and were characterized regarding their CO 2-gas sensitivity at different operation temperatures and gas environments. It was found that the sensors operate over a wide range of CO 2 concentrations. Interfering gases have only minor effects on the sensor response. By using miniaturized Al 2O 3-substrates as carriers for the sensitive nanocrystalline layer a significant decrease of the power and powder consumption for each sensor was achieved.