Highly intense violet-blue light emission at room temperature in structurally disordered SrZrO3 powders

Violet-blue photoluminescence was produced at room temperature in a structurally disordered SrZrO3 perovskite structure with a 350.7 nm excitation line. The intensity of this emission was higher than that of any other perovskites previously studied. The authors discuss the role of structural order-disorder that favors the self-trapping of electrons and charge transference, as well as a model to elucidate the mechanism that triggers photoluminescence. In this model the wide band model, the most important events occur before excitation. (c) 2007 American Institute of Physics.

Blue-green and red photoluminescence in CaTiO3 : Sm

Blue-green and red photoluminescence (PL) emission in structurally disordered CaTiO3:Sm (CT:Sm) powders was observed at room temperature with laser excitation at 350.7 nm. The perovskite-like titanate CT:Sm powders prepared by a soft chemical processing at different temperatures of annealing were structurally characterized by X-ray diffraction (XRD) and X-ray absorption near-edge structure (XANES). The results indicate that the generation of the broad PL band is related to order-disorder degree in the perovskitelike structure. (c) 2006 Elsevier B.V. All rights reserved.

Nanoscopic photoluminescence memory as a fingerprint of complexity in self-assembled alkyl/siloxane hybrids

A thermally activated photoluminescence memory effect, induced by a reversible order-disorder phase transition of the alkyl chains, is reported for highly organized bilayer alkyl/siloxane hybrids (see figure; left at room temperature, right at 120 degrees C). The emission energy is sensitive to the annihilation/formation of the hydrogen-bonded amide-amide array displaying a unique nanoscopic sensitivity (ca. 150 nm).

beta-ZnMoO4 microcrystals synthesized by the surfactant-assisted hydrothermal method: Growth process and photoluminescence properties

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

BaZrO3 Photoluminescence Property: An Ab Initio Analysis of Structural Deformation and Symmetry Changes

This article reports a theoretical study based on experimental results for barium zirconate, BaZrO3 (BZ) thin films, using periodic mechanic quantum calculations to analyze the symmetry change in a structural order-disorder simulation. Four periodic models were simulated using CRYSTAL98 code to represent the ordered and disordered BZ structures. The results were analyzed in terms of the energy level diagrams and atomic orbital distributions to explain and understand the BZ photoluminescence properties (PL) at room temperature for the disordered structure based on structural deformation and symmetry changes. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 111: 694-701, 2011

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)

Hierarchical Assembly of CaMoO4 Nano-Octahedrons and Their Photoluminescence Properties

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influence of the thermal treatment in the crystallization of NiWO4 and ZnWO4

NiWO4 and ZnWO4 were synthesized by the polymeric precursor method at low temperatures with zinc or nickel carbonate as secondary phase. The materials were characterized by thermal analysis (TG/DTA), infrared spectroscopy, UV-Vis spectroscopy and X-ray diffraction. NiWO4 was crystalline after calcination at 350 A degrees C/12 h while ZnWO4 only crystallized after calcination at 400 A degrees C for 2 h. Thermal decomposition of the powder precursor of NiWO4 heat treated for 12 h had one exothermic transition, while the precursor heat treated for 24 h had one more step between 600 and 800 A degrees C with a small mass gain. Powder precursor of ZnWO4 presented three exothermic transitions, with peak temperatures and mass losses higher than NiWO4 has indicating that nickel made carbon elimination easier.

Structural refinement and photoluminescence properties of irregular cube-like (Ca-1_Cu-x(x))TiO3 microcrystals synthesized by the microwave-hydrothermal method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A theoretical study on the photoluminescence of SrTiO3

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Strong violet-blue light photoluminescence emission at room temperature in SrZrO3: Joint experimental and theoretical study

Ultrafine ordered and disordered SrZrO3 powders were prepared by the polymeric precursor method. The structural evolution from structural disorder to order was monitored by X-ray diffraction and X-ray absorption near-edge spectroscopy. Complex cluster vacancies [ZrO5 center dot V-O(Z)] and [SrOII center dot V-O(Z)] (where V-O(Z) = V-O(X), V-O(center dot) and V-O(center dot center dot)) were proposed for disordered powders. The intense violet-blue light photoluminescence emission measured at room temperature in the disordered powders was attributed to complex cluster vacancies. High-level quantum mechanical calculations within the density functional theory framework were used to interpret the experimental results. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Photoluminescence in quasi-amorphous Pb0.8X0.2Zr0.53Ti0.47O3 (X = Ca, Sr and Ba) powders: An optical and structural study

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

Photoluminescence behavior in MgTiO3 powders with vacancy/distorted clusters and octahedral tilting

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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)

Rietveld refinement, morphology and optical properties of (Ba 1-xSrx)MoO4 crystals

In this article, the structural refinement, morphology and optical properties of barium strontium molybdate [(Ba1-x Sr x )MoO4 with x = 0, 0.25, 0.50, 0.75 and 1] crystals, synthesized by the co-precipitation (drop-by-drop) method, are reported. The crystals obtained were structurally characterized by X-ray diffraction (XRD), Rietveld refinement, and Fourier transform-Raman (FT-Raman) and Fourier transform-infrared (FT-IR) spectroscopies. The shapes of the crystals were observed by means of field-emission scanning electron microscopy (FE-SEM). The optical properties were investigated using ultraviolet-visible (UV-Vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD patterns, Rietveld refinement, and FT-Raman and FT-IR spectra showed that all of the crystals are monophasic with a scheelite-type tetragonal structure. The refined lattice parameters and atomic positions were employed to model the [BaO8], [SrO8] and [MoO4] clusters in the tetragonal lattices. The FE-SEM images indicate that increased x content produces a decrease in the crystal size and modifications in the crystal shape. UV-Vis spectra indicated a decrease in the optical band gap with an increase in x in the (Ba1-x Sr x )MoO4 crystals. Finally, a decrease in the intensity of PL emission is apparent with an increase in x up to 0.75 in the (Ba1-x Sr x )MoO4 crystal lattice when excited by a wavelength of 350nm, probably associated with the degree of structural order-disorder. © 2013 International Union of Crystallography Printed in Singapore - all rights reserved.