Influence of Sm3+ doping on the dielectric properties of CaCu3Ti4O12 ceramics synthesized via autocombustion

Ca-1 -xSmxCu3Ti4O12 (x = 0.0, 0.2, 03) electronic ceramics were fabricated via the chemical route using metal nitrate solutions in order to improve the dielectric properties of this ceramic. X-ray diffraction (XRD) analysis indicated the formation of a single CaCu3Ti4O12 (CCTO). Grain size of the samples doped with Sm3+ was in the range of 1-2 mu m, as opposed to 50-100 mu m in the pure samples of CCTO. The cutoff frequency with the doping was remarkably shifted, from 1 MHz (pure CCTO) to 10 MHz (doped CCTO). Meanwhile, the real dielectric (epsilon(r)) and imaginary dielectric (epsilon '') constants showed a decrease as the doping was increased. (C) 2013 Elsevier B.V. All rights reserved.

Study of pK Values and Effective Dielectric Constants of Ionizable Residues in Pentapeptides and in Staphylococcal Nuclease (SNase) Using a Mean-Field Approach

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

Investigation of the structural, optical and dielectric properties of highly (100)-oriented (Pb0.60Ca0.20Sr0.20)TiO3 thin films on LaNiO3 bottom electrode

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

Treatment of Reticulated Vitreous Carbon by Dielectric Barrier Discharge Plasma for Electrodes Production

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

Structural, dielectric, ferroelectric and optical properties of PBCT, PBST and PCST complex thin films on LaNiO3 metallic conductive oxide layer coated Si substrates by the CSD technique

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

Investigation of the dielectric relaxation processes in PbZr0.65Ti0.35O3-BaFe12O19 multiferroic ceramic composites

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

Acetylene plasma polymer treated by atmospheric dielectric barrier discharge

Plasma polymer films are very attractive for industrial applications in several sectors such as in the electronic, mechanic, biomedic, coating and others, due to its good adhesion, being insoluble in mild acids and bases and having a high crosslinking structure. This work reports the physical, structural, and surface properties of the polymer obtained from an acetylene plasma polymerization technique and treated by dielectric barrier discharge (DBD). The film was deposited in a reactor supplied by a radio-frequency power source at low pressure. After deposition, the nanofilms were treated in a DBD plasma reactor operating in air. The treatment times varied from 1 to 5 min. The analysis of molecular structure of the samples was investigated by FTIR spectroscopy, showing absorption bands in 3480, 2930, 1720, 1450 and 1380 cm(-1). The water contact-angle was investigated by goniometric technique and presented values from 5 to 65 degrees. The aging effect of these films was also studied. The alteration in the films surface morphology was assessed by an atomic force microscopy (AFM) which indicated that the roughness increased from 60 nm to 160 nm as a result of the DBD treatment. The refractive index of the samples presented values near 1.7, measured by UV-Visible spectroscopy. (C) 2014 Elsevier Ltd. All rights reserved.

Optimized design of substrate-integrated hollow waveguides for mid-infrared gas analyzers

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Production and characterization of Tm3+/Yb3+ codoped pedestal-type PbO-GeO2 waveguides

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Thickness-dependent piezoelectric behaviour and dielectric properties of lanthanum modified BiFeO3 thin films

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

Tailoring the refractive index of Ge-S based glass for 3D embedded waveguides operating in the mid-IR region

The photosensitivity of GeSx binary glasses in response to irradiation to femtosecond pulses at 800 nm is investigated. Samples with three different molecular compositions were irradiated under different exposure conditions. The material response to laser exposure was characterized by both refractometry and micro-Raman spectroscopy. It is shown that the relative content of sulfur in the glass matrix influences the photo-induced refractive index modification. At low sulfur content, both positive and negative index changes can be obtained while at high sulfur content, only a positive index change can be reached. These changes were correlated with variations in the Raman response of exposed glass which were interpreted in terms of structural modifications of the glass network. Under optimized exposure conditions, waveguides with positive index changes of up to 7.8x10−3 and a controllable diameter from 14 to 25 μm can be obtained. Direct inscription of low insertion losses (IL = 3.1 – 3.9 dB) waveguides is demonstrated in a sample characterized by a S/Ge ratio of 4. The current results open a pathway towards the use of Ge-S binary glasses for the fabrication of integrated mid-infrared photonic components.

Dielectric response of tungsten modified Ba(Ti0.90Zr0.10)O3 ceramics obtained by mixed oxide method

The electrical response of Ba(Ti0.90Zr0.10)O3 (BZT) ceramics obtained by the mixed oxide method as a functionof tungsten content was investigated. According to X-ray diffraction analysis the single phase BZT1W (1wt.% W doped BZT) and BZT2W (2 wt.% W doped BZT) ceramics, crystallized in a perovskite structure, wereobtained. It is also shown that tungsten substituted ceramics can be sintered at a reduced temperature whencompared to the undoped BZT. Electron paramagnetic resonance (EPR) analyses reveals that substitution ofTi4+ by W6+ causes distortion in the crystal structure changing lattice parameter. Substitution of W6+ on B-siteof ABO3 perovskite BZT ceramics shifted the phase transition to lower temperatures up to a tungsten contentof 2 wt.% leading to a relaxor-like behaviour.Keywords: donor dopant; ceramics; dielectric response; mixed oxide method

Dielectric behaviour of CaCu3Ti4O12-epoxy composites

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

Ferroelectric and dielectric characteristics of Bi3.25La0.75Ti3O12 thin films prepared by the polymeric precursor method

The ferroelectric properties and leakage current mechanisms of preferred oriented Bi3.25La0.75 Ti3O12 (BLT) thin films deposited on La0.5Sr0.5CoO3 (LSCO) by the polymeric precursor method were investigated. Atomic force microscopy indicates that the deposited films exhibit a dense microstructure with a rather smooth surface morphology. The improved ferroelectric and leakage current characteristics can be ascribed to the plate-like grains of the BLT films. © 2006 Trans Tech Publications, Switzerland.

Dielectric properties of Sr0.75Ba0.25Nb 2O6 thin films: Bias field, frequency and temperature dependence

Ferroelectric strontium barium niobate solid solutions had received great attention due to their excellent pyroelectric, electrooptic and photorefractive properties. Furthermore, they usually also present very interesting phase transition characteristics. In this work, polycrystalline single phase Sr 0.75 Ba 0.25 Nb 2 O 6 thin films were prepared by a hybrid chemical method and deposited on Pt/Ti/SiO 2 /Si substrates. The temperature dependence of dielectric constant was measured at different frequencies and bias field levels. The presence of two dielectric dispersion regions with relaxor characteristics was observed at distinct temperature ranges, corresponding to the ferro-paraelectric and to a structural phase transition at low temperatures, respectively. A specific dielectric dispersion region, associated with an incommensurate superstructure frequently observed in bulk samples, was not observed in this films probably due to their small grain sizes. © 2002 Taylor & Francis.