Intense visible photoluminescence in Ba(Zr0.25Ti0.75)O-3 thin films

Photoluminescence at room temperature in Ba(Zr0.25Ti0.75)O-3 thin films was explained by the degree of structural order-disorder. Ultraviolet-visible absorption spectroscopy, photoluminescence, and first principles quantum mechanical measurements were performed. The film annealed at 400 degrees C for 4 h presents intense visible photoluminescence behavior at room temperature. The increase of temperature and annealing time creates [ZrO6]-[TiO6] clusters in the lattice leading to the trapping of electrons and holes. Thus, [ZrO5]-[TiO6]/[ZrO6]-[TiO6] clusters were the main reason for the photoluminescence behavior.

Study of structural evolution and photoluminescent properties at room temperature of Ca(Zr, Ti)O-3 powders

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Al3+ environments in nanostructured ZnAl2O4 and their effects on the luminescence properties

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

SnO2 nanocrystals synthesized by microwave-assisted hydrothermal method: towards a relationship between structural and optical properties

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Radio luminescence properties of decaoctahedral BaZrO3

Radioluminescence (RL) emissions were obtained for the BaZrO3 self-assembled nanocrystals under decaoctahedral shape, if produced via microwave-assisted hydrothermal method. Trapped F centers created within the band gap are the result of order-disorder effects, which act as key factors supporting significant RL emission through a detrapping process. The influences of size and morphology on RL properties are take into account. No radiation damage or loss of emission intensity was observed. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Amorphous manganese polyphosphates: preparation, characterization and incorporation of azo dyes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Upconversion luminescence in Er3+ doped and Er3+/Yb3+ codoped zirconia and hafnia nanocrystals excited at 980 nm

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Visible emission from Er-doped SnO2 thin films deposited by sol-gel

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

Blue cooperative luminescence in Yb3+-doped tellurite glasses excited at 1.064 mu m

Blue luminescence emission around 480 nm through cooperative upconversion from pairs of Yb3+ ions implanted into 60TeO(2)-10GeO(2)-10K(2)O-10Li(2)O-10Nb(2)O(5) tellurite glasses and excited by a cw laser at 1.064 mum is demonstrated. Cooperative luminescence emission enhancement owing to the temperature dependent multiphonon-assisted anti-Stokes excitation process of the ytterbium ions is also observed. The experimental results revealed a fourfold enhancement in the cooperative luminescence emission when the sample was heated in the temperature range of 20 degreesC-260 degreesC. The thermally induced enhancement is assigned to the effective absorption cross-section for the ytterbium ions which is an increasing function of the medium temperature. (C) 2002 American Institute of Physics.

Luminescence quenching by iron in barium aluminoborate glasses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ytterbium-induced energy-transfer upconversion enhancement in Nd3+/Pr3+-codoped PbGeO3-PbF2-CdF2 glass excited at 810nm

The effect of ytterbium ions upon energy transfer (ET) excited upconversion emission in Nd3+/Pr3+ -codoped PbGeO3-PbF2-CdF2 glass under 810 nm diode laser excitation is investigated. The results revealed that the presence of Yb3+ ions in the Nd3+/Pr3+-doped sample yields a fourfold enhancement in the visible and near infrared upconversion luminescence. The dependence of the upconversion process upon the excitation power, Nd3+, and Yb3+ concentrations is examined. The results indicated that ytterbium plays a major role in the ET upconversion process by bridging the 810nm neodymium excitation to praseodymium ions. The population of the Pr3+ ions P-3(0) emitting level was accomplished through a multi-ion interaction involving ground-state and excited-state absorption of pump photons at 810 nm by the Nd3+ followed by successive ET involving the Nd3+-Yb3+ and Yb3+-Pr3+ pairs. There is also direct ET Nd3+-Pr3+. (c) 2005 Elsevier B.V. All rights reserved.

Photoluminescence at room temperature in amorphous SrTiO3 thin films obtained by chemical solution deposition

Intense photoluminescence in highly disordered strontium titanate amorphous thin films prepared by the polymeric precursor method was observed at room temperature (300 K). The luminescence spectra of SrTiO3 amorphous thin films at room temperature revealed an intense single-emission band in the visible region. X-ray absorption near edge structure was used to probe the local atomic structure of SrTiO3 amorphous and crystalline thin films. Photoluminescence intensity in the 535 nm range was found to be correlated with the presence of non-bridging oxygen defects. A discussion is presented of the nature of this photoluminescence, which may be related to the disordered structure in SrTiO3 amorphous thin films. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Reversible holographic glasses using visible lasers

Antimony based glasses have been investigated for the first time regarding the possibility of holographic data storage using visible lasers sources. Changes in both refractive index and the absorption coefficient were measured using a holographic setup. The modulation of the optical constants is reversible by heat treatment. Bragg gratings were written under visible light of an Ar laser and erased thermally.

Photo luminescence: A probe for short, medium and long-range self-organization order in ZrTiO4 oxide

Photoluminescent disordered ZrTiO4 powders were obtained by the polymeric precursor soft-chemical method. This oxide system (ordered and disordered) was characterized by photoluminescence, Raman spectroscopy, X-ray diffraction, differential scanning calorimetry and UV vis absorption experiments. The UV absorption tail formation in the disordered oxides was related to the diminution of optical band gap. In the disordered phase, this oxide displayed broad band photoluminescence caused by change in coordination number of titanium and zirconium with oxygen atoms. The gap decreased from 3.09 eV in crystalline oxide to 2.16 eV in disordered oxide. The crystalline oxide presented an orthorhombic alpha-PbO2-type structure in which Zr4+ and Ti4+ were randomly distributed in octahedral coordination polyhedra with oxygen atoms. The amorphous-crystalline transition occurred at almost 700 degrees C, at which point the photoluminescence vanished. The Raman peak at close to 80-200 cm(-1) indicated the presence of locally ordered Ti-O-n and Zr-O-n polyhedra in disordered photoluminescent oxides. (c) 2006 Elsevier B.V. All rights reserved.

Visible PL phenomenon at room temperature in disordered structure of SrWO4 powder

The SrWO4 (SWO) powders were synthesized by the polymeric precursor method and annealed at different temperatures. The SWO structure was obtained by X-ray diffraction and the corresponding photoluminescence (PL) spectra was measured. The PL results reveal that the structural order-disorder degree in the SWO lattice influences in the PL emission intensity. Only the structurally order-disordered samples present broad and intense PL band in the visible range. To understand the origin of this phenomenon, we performed quantum-mechanical calculations with crystalline and order-disordered SWO periodic models. Their electronic structures were analyzed in terms of band structure. The appearance of localized levels in the band gap of the order-disordered structure was evidenced and is a favorable condition for the intense PL to occur.