Evaluation of the effect of the stoichiometric ratio of Ca/Cu on the electrical and microstructural properties of the CaCu3Ti4O12 polycrystalline system

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of the microwave oven on structural, morphological and electrical properties of SrBi4Ti4O15 thin films grown on Pt/Ti/SiO2/Si substrates by a soft chemical method

Thin films of SrBi4Ti4O15 (SBTi), a prototype of the Bi-layered-ferroelectric oxide family, were obtained by a soft chemical method and crystallized in a domestic microwave oven. For comparison, films were also crystallized in a conventional method at 700 degrees C for 2 h. Structural and morphological characterization of the SBTi thin films were investigated by Xray diffraction (XRD) and atomic force microscopy (AFM), respectively. Using platinum coated silicon substrates, the ferroelectric properties of the films were determined. Remanent polarization P-r and a coercive field E-c values of 5.1 mu C/cm(2) and 135 kV/cm for the film thermally treated in the microwave oven and 5.4 mu C/cm(2) and 85 kv/cm for the film thermally treated in conventional furnace were found. The films thermally treated in the conventional furnace exhibited excellent fatigue-free characteristics up to 10(10) switching cycles indicating that SBTi thin films are a promising material for use in non-volatile memories. (C) 2007 Elsevier B.V. All rights reserved.

Effect of oxidizing atmosphere on the electrical properties of SrBi4Ti4O15 thin films obtained by the polymeric precursor method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Enhanced ferroelectric properties of La-substituted BiFeO3 thin films on LaSrCoO3/Pt/TiO2/SiO2/Si (100) substrates prepared by the soft chemical method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electric and dielectric behavior of CaCu3Ti4O12-based thin films obtained by soft chemical method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of vanadium on electrical and microstructural properties of CaCu3Ti4O12/CaTiO3

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Surface characteristics analysis of polypropylene treated by dielectric barrier discharge at atmospheric pressure

Polypropylene (PP) samples were treated by Dielectric Barrier Discharge (DBD) in order to modify their surface characteristics. The XPS analysis reveals that the DBD treatment added oxygen atoms to the PP surface. These polar groups cause increase in the wettability as shown by water contact angle measurements. The formation of low-molecular-weight oxidized materials (LMWOMs) in the form of small nodules on the PP surface was observed by atomic force microscopy (AFM). The presence of oxygen polar groups on the PP surface was also confirmed by infrared spectroscopy (FTIR). All analysis were performed before and after rinsing the treated samples in water and showed that the LMWOM can be removed from the surface by polar solvents.

On the characterisation of electrically stressed polyethylene before and after chemical treatment

Low-density polyethylene (LDPE) was characterised for its dielectric and electrical properties before and after chemical treatment. A reduction in the permittivity and dielectric loss was observed in the polymer after treatment with hexane. The intensity in the Raman Spectrum in the disordered longitudinal acoustic mode region (DLAM) also was reduced due to a hexane treatment. Using thermally stimulated discharge current (TSDC) and laser-intensity-modulated method (LIMM) techniques it was observed that charge injection can be enhanced in the polymer matrix in the empty sites, created by the removal of the low molecular weight impurities with chemical treatment. (C) 2002 Kluwer Academic Publishers.

Mesoscopic structure evidenced by AC dielectric nonlinearities in Sr(0.75)Ba(0.25)Nb(2)O(6) relaxor ferroelectric thin films

The AC electric field and temperature dependences of the dielectric permittivity for strontium barium niobate (Sr(0.75)Ba(0.25)Nb(2)O(6)) relaxor ferroelectric thin films have been investigated. The results indicate the existence of a true mesoscopic structure evidenced by the nonlinear dielectric response of these films, which is similar to those observed for bulk relaxor ferroelectrics. A tendency for a temperature dependent crossover from a linear to a quadratic behaviour of the dielectric nonlinearity was observed, indicating an evolution from paraelectric to glass-like behaviour on cooling the samples towards the freezing temperature transition.

Effect of polyol excess on the electrical property of vegetable-polyurethane film

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

DC Electric Field Dependence of the Dielectric Constant of Pzt Thin Films Prepared by Polymeric Precursor Method

This work reports dielectric measurements performed on Pb(Zr0.53Ti0.47)O3 (PZT) thin films prepared by a polymeric precursor method. The -E curves obtained for the PZT film measured at 100 kHz, under a small ac 0.2 kV/cm signal-test and a dc scan featured a typical butterfly curve. However, the -E curves obtained for PZT film under a dc scan, with a scan rate of 0.003 V/s, shows a pronounced asymmetry. The absence of a symmetric secondary peak in -E curves could be an indication of essentially 180 domain switching.

Domain wall contribution to dielectric and piezoelectric responses in 0.65Pb(Mg1/3Nb2/3)-0.35PbTiO(3) ferroelectric ceramics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Piezo and Dielectric Properties of PHB-PZT Composite

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Investigation of nonlinear dielectric properties in Sr0.75Ba0.25Nb2O6 relaxor ferroelectric thin films

The ac and dc driving fields dependence of the dielectric permittivity for the strontium barium niobate relaxor ferroelectric thin films has been investigated. The nonlinear dielectric properties were obtained by using the measurements of the dielectric permittivity of the material as a function of the ac and dc "bias" electric field amplitude in wide frequency (100 Hz-10 MHz) and temperature (50-450 K) intervals. The results hint the existence of a true mesoscopic dielectric relaxor response in the ferroelectric thin film, which is very similar to those observed in bulk relaxor ferroelectrics. An anomalous behavior of the NL dielectric response was observed when submitted to moderate dc electric fields levels,,indicating a crossover from paraelectric to a glasslike behavior on cooling the sample toward the freezing transition. The obtained results were analyzed within the framework of the models proposed in the current literature.

(1-x)PMN-xPT ceramics prepared by conventional and modified columbite route: Effect on electrical properties

This study aims to demonstrate how the chemical homogeneity of B cations affects the microstructure and electrical responses of (1-x) PMN-xPT ceramics. Two methodologies were employed to synthesize three different compositions, with x assuming the values 0.10, 0.28, and 0.35. If compared to conventional method, the Ti-modified columbite route, which is characterized by higher B cation homogeneity, leads to PMN-PT powders and ceramics with lower content of PNT pyrochlore phase and, for 0.65PMN-0.35PT composition, minor amount of tetragonal phase is found. Conclusively, PMN-PT ceramics obtained by modified route favors B cations homogeneity, enhancing the dielectric, ferroelectric and piezoelectric properties.