Synthesis, growth process and photoluminescence properties of SrWO4 powders

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Wettability and photodegradation activity of sol-gel dip-coated zinc oxide films

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synthesis, structural refinement and optical behavior of CaTiO3 powders: A comparative study of processing in different furnaces

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synthesis, ferroelectric and optical properties of (Pb,Ca)TiO3 thin films by soft solution processing

Calcium modified lead titanate sol was synthesized using a soft solution processing, the so-called polymeric precursor method. In soft chemistry method, soluble precursors such as lead acetate trihydrate, calcium carbonate and titanium isopropoxide, as starting materials, were mixed in aqueous solution. Pb0.7Ca0.3TiO3 thin films were deposited on platinum-coated silicon and quartz substrates by means of the spinning technique. The surface morphology and crystal structure, dielectric and optical properties of the thin films were investigated. The electrical measurements were conducted on metal-ferroelectric-metal (MFM) capacitors. The typical measured small signal dielectric constant and dissipation factor at a frequency of 100 kHz were 299 and 0.065, respectively, for a thin film with 230 nm thickness annealed at 600degreesC for 2 h. The remanent polarization (2P(r)) and coercive field (E-c) were 32 muC/cm(2) and 100 kV/cm, respectively. Transmission spectra were recorded and from them, refractive index, extinction coefficient, and band gap energy were calculated. Thin films exhibited good optical transmissivity, and had optical direct transitions. The present study confirms the validity of the DiDomenico model for the interband transition, with a single electronic oscillator at 6.858 eV. The optical dispersion behavior of PCT thin film was found to fit well the Sellmeir dispersion equation. The band gap energy of the thin film, annealed at 600degreesC, was 3.56 eV. The results confirmed that soft solution processing provides an inexpensive and environmentally friendly route for the preparation of PCT thin films.

Photoexpansion and photorefraction in oxysulphide glasses

Oxysulphide glasses have been prepared in the pseudo binary system GeS(2.6)-Ga(2)O(3). The effect of addition of gallium oxide has been evaluated in term of thermal and optical properties. Structural behavior has been studied using Raman spectroscopy. Samples have been exposed above band gap energy (3.52 eV) varying power density and exposure time. Giant photoexpansion and photorefraction is obtained for samples containing 20% of Ga(2)O(3). (C) 2009 Elsevier B.V. All rights reserved.

A new processing method of CaZn2(OH)(6)center dot 2H(2)O powders: Photoluminescence and growth mechanism

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Cluster Coordination and Photoluminescence Properties of alpha-Ag2WO4 Microcrystals

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structure and optical properties of [Ba1-xY2x/3](Zr0.25Ti0.75)O-3 powders

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

Synthesis and photoluminescence behavior of Bi4Ti3O12 powders obtained by the complex polymerization method

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Photoluminescent behavior of BaWO4 powders processed in microwave-hydrothermal

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

(Sr,Tm)ZrO3 powders prepared by the polymeric precursor method: Synthesis, optical properties and morphological characteristics

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Intense and broad photoluminescence at room temperature in structurally disordered Ba[Zr0.25Ti0.75]O-3 powders: An experimental/theoretical correlation

Intense and broad photoluminescence (PL) emission at room temperature was observed on structurally disordered Ba[Zr0.25Ti0.75]O-3 (BZT) powders synthesized by the polymeric precursor method. BZT powders were annealed at 573 K for different times and at 973 K for 2 h in oxygen atmosphere. The single-phase cubic perovskite structure of the powder annealed at 973 K for 2 It was identified by X-ray diffraction and Fourier transform Raman techniques. PL emission increased with the increase of annealing time, which reached its maximum value in the powder annealed at 573 K for 192 h. First principles quantum mechanical calculations based on density functional theory (B3LYP level) were employed to study the electronic structure of ordered and disordered models. The theoretical calculations and experimental measurements of Ultraviolet-visible absorption spectroscopy indicate that the presence of intermediary energy levels in the band gap is favorable for the intense and broad PL emission at room temperature in disordered BZT powders. The PL behavior is probably due the existence of a charge gradient on the disordered structure, denoted by means of a charge transfer process from [TiO5]-[ZrO6] or [TiO6]-[ZrO5] clusters to [TiO6]-[ZrO6] clusters. (C) 2008 Elsevier Ltd. All rights reserved.

Ga-Modified Nanostructured ZnO: Characterization and Application in Dye-Sensitized Solar Cells

ZnO has received great attention in many applications due to its electronic and optical properties. We report on the preparation of ZnO and gallium-containing ZnO (ZnO:Ga) nanoparticles by the precipitation method. The nanoparticles have the wurtzite structure and a high crystallinity. Gallium ions are present as Ga(3+), as evidenced by the binding energies through XPS. Porosity and surface area of the powder increased under increasing gallium level, explained by the smaller particle size of ZnO:Ga samples compared with ZnO. The estimated optical band gap of ZnO was 3.2 eV, comparable to ZnO:Ga.

Structural refinement, optical and microwave dielectric properties of BaZrO3

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

Effect of different surfactants on the shape, growth and photoluminescence behavior of MnWO4 crystals synthesized by the microwave-hydrothermal method

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