Effects of annealing on the crystallization and roughness of PLZT thin films

Lead lanthanum zirconate titanate (PLZT) thin films with stoichiometry (9/65/35) were prepared by a dip-coating process using a polymeric organic solution. The solution viscosity was adjusted in the range of 15-56 cP. Silicon (100) substrates were previously cleaned and then immersed in the solution. The withdrawal speed of substrate from the solution was adjusted within a range of 5 to 20 mm/min. The coated substrates were thermally treated in the 450-700 degreesC temperature range. Surface roughness and crystallization of these films are strongly dependent on the annealing conditions. Infrared and X-ray diffraction data for PLZT powders heat-treated at 650 degreesC for 3 h show that the material is free of carbonate phases and crystalline. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Influence of oxygen flow on crystallization and morphology of PLZT thin films

PLZT thin films were prepared by a dip coating process using Pechini's method, also known as polymeric precursor method. The PLZT solution was obtained from a mixture of the individual cation solutions and the process to prepare each solution is based on metallic citrate polymerization. The viscosity of the PLZT solution was adjusted at 40 cP while the ionic concentration was adjusted at 0.1 M. PLZT solutions were deposited on silicon (100) and platinum coated silicon (100) substrates with withdrawal speed at 5 mm/min. The coated substrates were thermally treated with a heating rate of 1 degreesC/min up to 300 degreesC and 5 degreesC/min up to 650 degreesC in order to obtain homogeneous and cracks free films. The influence of oxygen flow on crystallization and morphology of PLZT (9/65/35) thin film is discussed. (C) 2002 Elsevier B.V. Ltd and Techna S.r.l. All rights reserved.

Influence of thickness on crystallization and properties of LiNbO3 thin films

Thin films of lithium niobate were deposited on Pt/Ti/SiO2 (111) substrates by spin coating from the polymeric precursor method (Pechini process). Annealing in static air was performed at 500 degreesC for 3 h. The obtained films were characterized by X-ray diffraction and atomic force microscopy. The dielectric constant, dissipation factor and resistance were measured in frequency region from 10 Hz to 10 MHz and the hysteresis loop was obtained. The influence of number of layers on crystallization, morphology and properties of LiNbO3 thin films is discussed. (C) 2003 Elsevier B.V. All rights reserved.

Relationship between structural features and in vitro release of doxorubicin from biocompatible anionic microemulsion

In this work structural features of anionic microemulsions, containing the pharmaceutical biocompatible components soya phosphatidylcholine (SPC), eumulgin HRE 40 (EU) and sodium oleate (SO) as surfactant, cholesterol (CHO) as oil phase and aqueous buffer were studied. Microemulsions were formulated with and without the antitumor drug doxorubicin (DOX). The various microstructures characterized in the pseudo-temary phase diagram were analyzed by polarized light microscopy, small-angle X-ray scattering (SAXS) and X-ray diffraction (XRD) as well as by their ability to incorporate and release DOX. The experimental results demonstrated a correlation between the composition, the structural features and drug delivery. It was found that at higher cholesterol contents, the crystallization of CHO polymorph phases changed the mobility of DOX molecules. Droplets were formed with short-range spatial correlation from a microemulsion (ME) with a low surfactant:oil ratio. More ordered structures with lamellar arrangements formed by the increasing of the CHO proportions in the formulation may be due to CHO crystallization. The in vitro release of DOX showed that the presence of a high content of crystalline CHO prolongs the release of DOX from ME. The retention of DOX in the internal oil phase of the ME may modulate the drug release for a prolonged time. These results clearly demonstrate the potential of ME as a drug-delivery system. (c) 2007 Elsevier B.V. All rights reserved.

Influence of oxygen atmosphere on crystallization and properties of LiNbO3 thin films

Thin films of lithium niobate were deposited on the Pt/Ti/SiO2 (111) substrates by spin coating from the polymeric precursor method (Pechini process). Annealing in static air and oxygen atmosphere was performed at 500 degreesC for 3 h. The films obtained were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The dielectric constant and dissipation factor were measured in frequency region from 10 Hz to 10 MHz. Electrical characterization of the films pointed to ferroelectricity via hysteresis loop. The influence of oxygen atmosphere on crystallization, morphology and properties of LiNbO3 thin films is discussed. (C) 2003 Elsevier Ltd. All rights reserved.

Structural Investigations of Glass Ceramics in the Ga2S3-GeS2-CsCl System

Transparent glass ceramics have been prepared in the Ga2S3-GeS2-CsCI pseudoternary system appropriate heat treatment time and temperature. In situ X-ray diffraction at the heat treatment temperature and Cs-133 and Ga-71 solid-state nuclear magnetic resonance have been performed in function of annealing time to understand the crystallization process. Both techniques have evidenced the nucleating agent role played by gallium with the formation of Ga2S3 nanocrystals. on the other hand, cesium is incorporated very much later into the crystallites during the ceramization. Moreover, the addition of CsCl, which is readily integrated into the glassy network, permits us to shift the optical band gap toward shorter wavelength. Thus, new glass ceramics transmitting in the whole visible range up to 11.5 mu m have been Successfully synthesized from the (Ga2S3)(35)-(GeS2)(25)-CsCl40 base glass composition.

Crystallization study of molybdate phosphate glasses by thermal analysis

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

Spatial variability of the physical and mineralogical properties of the soil from the areas with variation in landscape shapes

Este trabalho teve como objetivo avaliar a influência das formas do relevo na variabilidade espacial de atributos físicos e suas relações com a mineralogia da argila de um Latossolo Vermelho eutroférrico, utilizando a técnica da geoestatística. Os solos foram amostrados nos pontos de cruzamento de uma malha, com intervalos regulares de 10 m, nas profundidades de 0,0-0,2 m, 0,2-0,4 m e 0,4-0,6 m para os atributos físicos e 0,6-0,8 m para os atributos mineralógicos. Os valores médios para a densidade do solo e resistência do solo à penetração são maiores no compartimento I onde a relação Ct/Ct+Gb é relativamente maior, indicando a presença de maior teor de caulinita. No compartimento II a condutividade hidráulica e a macroporsidade são maiores, influenciados provavelmente pelo predomínio da gibbsita. Portanto, conclui-se que a identificação das pedoformas é muito eficiente para compreender a variabilidade espacial de propriedades do solo. Sendo que, as variações na forma da paisagem promovem variabilidade espacial diferenciada das propriedades físicas e mineralógicas do solo.

Obtenção in situ do compósito alfa-SiAlON-SiC

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

Time dependence and energy-transfer mechanisms in Tm3+Ho3+ and Tm3+-Ho3+ co-doped alkali niobium tellurite glasses sensitized by Yb3+

Glass samples with the composition (mol%) 80TeO(2)-10Nb(2)O(5)-5K(2)O-5Li(2)O, stable against crystallization, were prepared containing Yb3+, Tm3+ and Ho3+. The energy transfer and energy back transfer mechanisms in samples containing 5% Yb3+-5% Tm3+ and 5% Yb3+-5% Tm3+-0.5% Ho3+ were estimated by measuring the absorption and fluorescence spectra together with the time dependence of the Yb3+ F-2(5/2) excited state. A good fit for the luminescence time evolution was obtained with the Yokota-Tanimoto's diffusion-limited model. The up-conversion fluorescence was also studied in 5% Yb-5% Tm. 5% Yb-0.5% Ho and 5% Yb-5% Tm-0.5% Ho tellurite glasses under laser excitation at 975 nm. Strong emission was observed from (1)G(4) and F-3(2) Tm3+ energy levels in all samples. The S-5(2) Ho3+ emission was observed only in Yb3+Ho3+ samples being completely quenched in Yb3+/Tm3+/Tm3+ samples. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Photo-induced transformations in chalcogenide nanocomposite layers

Investigations of photo-induced structural transformations (PST) and related changes of optical parameters in amorphous chalcogenide layers were further developed towards the establishment of their dependence on the compositional modulation of the material at nanoscale-dimensions (similar to3-10 nm) and possible improvement of optical recording parameters as well. Besides the known amorphous-amorphous PST, photo-stimulated interdiffusion and crystallization in multilayer structures were found as a useful method for amplitude-phase optical relief formation. The last two types of PST were influenced by size restrictions and efficiently operated by the composition and by the modulation period of the layered nanocomposite. Experimental evidences were obtained in Se-, AsSe-, Se0.4Te0.6-containing layered or quasi zero-dimensional structures based on As2S3 or SiOx and MgF2 matrix. Comparison was made with As2S3- and GeS2-based multicomponent layers, containing Se, Te and Ga. (C) 2004 Elsevier B.V. All rights reserved.

Structure and crystallization of lanthanum fluorozirconate glasses

Glasses with compositions (1-x)ZrF4-xLnF(3), 0.2 less than or equal to x less than or equal to 0.4 and Ln = La or La, Eu have been synthesized and investigated using differential scanning calorimetry, X-ray diffraction, Raman scattering and Eu3+ optical spectroscopy. Single-phase polycrystalline lanthanum fluorozirconates with Zr/Ln ratio equal to 1, 2 and 3 have been investigated using the same techniques for comparison. The crystalline phases LnZrF(7), LnZr(2)F(11), LT-LnZr(3)F(15) (orthorhombic) and HT-LnZr(3)F(15) (trigonal) have been characterized in the recrystallized glasses and in samples spontaneously crystallized from the melt. Another phase has also been observed but remains undefined, the Raman scattering spectra of the vitreous samples are related to the vibration modes of [ZrF6] isolated octahedra, and of [ZrF7] and [ZrF8] structural units with bridging fluorine ions. The Eu3+ fluorescence data are related to a predominant local environment of the lanthanide ions in the glasses similar to that of the lanthanide in LnZrF(7).

Er3+ and Eu3+ containing transparent glass ceramics in the system PbGeO3-PbF2-CdF2

Glasses with composition 60PbGeO(3)-10PbF(2)-30CdF(2) (mol%) have been obtained in the bulk form with a high stability against crystallization. After doping them with 0.5 mol% of Er3+ or Eu3+ and appropriate heat treatment transparent glass ceramics could be obtained. Electronic spectroscopy, X-ray diffraction and transmission electron microscopy measurements have been made. beta-PbF2: Er3+/Eu3+ Single crystals, 5-10 nm in size, are detected in the otherwise transparent composite medium, the size of the particles and absence of clustering allowing for the increased transparency of the final materials. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Crystallization kinetic of fluoro-zirconate glasses by non-isothermal analysis

Fluoride glasses have been extensively studied due to their high transparency in the infrared wavelength. The crystallization kinetics of these systems has been studied using DTA and DSC techniques. Most of the experimental data is frequently investigated in terms of the Johnson-Mehl-Avrami (JMA) model in order to obtain kinetic parameters.In this work, DSC technique has been used to study the crystallization of fluorozirconate glass under non-isothermal conditions. It was found that JMA model was not fit to be applied directly to these systems, therefore, the method proposed by Malek has been applied and the Sestak-Berggren (SB) model seems to be adequate to describe the crystallization process.

New crystal forms of Diocleinae lectins in the presence of different dimannosides

Studying the interactions between lectins and sugars is important in order to explain the differences observed in the biological activities presented by the highly similar proteins of the Diocleinae subtribe. Here, the crystallization and preliminary X--ray data of Canavalia gladiata lectin (CGL) and C. maritima lectin (CML) complexed with Man(alpha 1-2)Man(alpha 1)OMe, Man(alpha 1-3)Man(alpha 1)OMe and Man(alpha 1-4)Man(alpha 1)OMe in two crystal forms [the complexes with Man(alpha 1-3)Man(alpha 1)OMe and Man(alpha 1-4)Man(alpha 1)OMe crystallized in space group P3(2) and those with Man(alpha 1-2)Man(alpha 1)OMe crystallized in space group I222], which differed from those of the native proteins (P2(1)2(1)2 for CML and C222 for CGL), are reported. The crystal complexes of ConA-like lectins with Man(alpha 1-4)Man(alpha 1)OMe are reported here for the first time.