The role of oxygen vacancy in the photoluminescence property at room temperature of the CaTiO3

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

EPR of Mn as densifying agent in SnO2 powders

Electron Paramagnetic Resonance (EPR) spectra have been obtained at room temperature and at X-band in powders of SnO2 doped with Mn from 0.3 to 10% and submitted to heat treatment from 500 to 900 °C. Mn ions are probably located at particle surfaces as Mn2+, evidenced by its single EPR line which narrows by the exchange interaction effect due to particle growth observed by the BET technique. In samples doped above 1% formation Of Mn3O4 is detected on particle surfaces and a small quantity of Mn is thermally diffused into the bulk as Mn4+. Powders compacted and sintered at 1300 °C confirmed that Mn2+ ions remain at grain boundaries acting as densifying agent.

Observation of piezoelectric response on tungsten doped barium zirconium titanate ceramics

This study describes observation of piezoelectric response of Ba(Zr 0.10Ti 0.90.O3 ceramics modified with tungsten (BZT:2W) by the mixed oxide method. According to X ray diffraction analysis, the ceramics are free of secondary phases. Transmission electron microscopy (TEM) analyses reveals the absence of segregates in the grain boundaries indicates the high solubility of WO3 in the BZT matrix. The dielectric permittivity measured at a frequency of 10 KHz was equal to 6500 with dieletric loss of 0.15. A typical hysteresis loop was observed at room temperature. Electron Paramagnetic Resonance (EPR) analyses reveals that substitution of W6+ by Ti4+ causes distortion in the crystal structure changing lattice parameter. Polarization reversal was investigated by applying dc voltage through a conductive tip during the area scanning. Piezoelectric force microscopy images reveals that in-plane response may not change its sign upon polarization switching, while the out-of-plane response does. Copyright © 2010 American Scientific Publishers.

Production and characterization of Tm3+/Yb3+ codoped waveguides based on PbO-GeO2 thin films

Fabrication and optical characterization of Tm3+/Yb3+ codoped PbO-GeO2 (PGO) pedestal-type waveguides are investigated in this work. It is important to mention that, to the best of authors' knowledge, the use of PGO pedestal-type waveguide has not been studied before. PGO thin films codoped with Tm3+ and Yb3+ were obtained through RF magnetron sputtering technique. The pedestal profile was obtained using conventional optical lithography procedures, followed by plasma etching and sputtering deposition. The profile of Tm3+/Yb3+ codoped PGO waveguides was observed by means of Scanning Electron Microscopy (SEM) measurements. Also the infrared and infrared-to-visible frequency upconversion luminescences of Tm3+ ions were measured exciting the samples with a cw 980 nm diode laser. Propagation losses around 11 dB/cm and 9 dB/cm were obtained at 630 and 1050 nm, respectively, for waveguides in the 20-100 μm width range. Single-mode propagation was observed for waveguides width up to 12 μm and 7 μm, at 1050 nm and 630 nm, respectively; larger waveguides width provided multi-mode propagation. The present results corroborate the possibility of using Tm3+/Yb3+ codoped PGO thin films as active waveguide for photonic applications. © 2013 Elsevier B.V. All rights reserved.

Sistemas de liberação controlada de óxido nítrico baseados em ditiocarbamatos

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

Síntese, caracterização e investigação das atividades biológicas de complexos de cobre(II) contendo moléculas bioativas e ligantes nitrogenados

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Investigação da atividade biólogica de complexos de Cobre (II) contendo ligantes nitrogenados

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ressonância paramagnética eletrônica (RPE) aplicada em semicondutores orgânicos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Transição vesícula-micela em misturas de dispersões de vesículas com soluções de micelas

Pós-graduação em Biofísica Molecular - IBILCE

Sensores sólidos para detecção de óxido nítrico baseados em cucurbit[6]uril e em siloxano-poli(oxipropileno)

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

Estudo da interação da natamicina com membranas fosfolipídicas incorporadas de esteróis

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structure and thermal behavior of PMMA-polysilsesquioxane organic-inorganic hybrids

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

An investigation into the influence of zinc precursor on the microstructural, photoluminescence, and gas-sensing properties of ZnO nanoparticles

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Correlation between structural and electronic order-disorder effects and optical properties in ZnO nanocrystals

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

Transformações de Lorentz e seus invariantes

In this paper, we will show the types of Lorentz transformations, from the most described in books, special Lorentz transformation that relates two inertial systems whose relative velocities are directed along an axis of the respective bases systems. However, we will see a peculiarity that goes unnoticed in this transformation, although they have reported in many books a parallel between the transformation inertial systems, due to the fact that the speed is parallel to an axis, it is actually a semi-parallel processing. The next transformation that we will see is one in which a system moves with a relative speed that has arbitrary direction with respect to a given system, we will show that this transformation may be appointed as non-rotational Lorentz transformation. Before obtain, the later type of transformation, the rotational Lorentz transformation, which is the interface between Special Relativity and General Relativity, we will describe the systems to be rotated, not just inertial systems, show what the characteristics are that define the non-rotational and rotational transformations. The in last topic of this chapter we will also show how the idea of Thoma’s theorythat uses this transformation to create what he defines as the proper coordinate axes of the particleused to obtain the factor 1/2 electron spin. In the last chapter we show how the Lorentz invariants are obtained, quantities measures that are also in different Lorentz reference, with the focus on mass that has erroneously been described in many books, that varies according to the agreement reference system