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1.
(Lu 1–xEu x) 2O 3 smooth, crack‐free, transparent films were prepared by the Pechini sol–gel method and a spin‐coating technique. Thermogravimetric analysis, differential thermal analysis and FITR spectroscopy were used to study the chemical processes during annealing of the films. Film structure, morphology and optical properties were investigated. X‐ray diffraction (XRD) analysis reveals the cubic phase of (Lu 1–xEu x) 2O 3 films annealed in the 600–1000 °C temperature range. Smooth and crack‐free films with thicknesses of 250–1000 nm were obtained in the 600–800 °C temperature range. The thickness upper limit (1000 nm) of morphological stability of films (Lu 1–xEu x) 2O 3 on sapphire substrates has been studied. 相似文献
2.
Silica submicron spherical particles coated with an yttrium aluminum garnet (Y 3Al 5O 12, YAG) layer doped with Eu 3+ were prepared by the sol–gel method. The structure and morphology of samples determined by the X-ray powder diffraction measurements and transmission electron microscope images, respectively, indicated that well-crystallized garnet nanocrystallites were formed with successive coating cycles. Similar trends were deduced from the evolution of the luminescence spectra. The ratio of integrated intensities of the 5D 0 → 7F 2 and 5D 0 → 7F 1 transitions was used to analyze the structural variations in the surroundings of the Eu 3+ ion. The effect of coating was analyzed by comparing the luminescence properties of the Y 3Al 5O 12:Eu 3+ nanocrystalline powders and composite Y 3Al 5O 12:Eu 3+/SiO 2 materials. 相似文献
3.
The influence of the size of Y2O3 powder particles on the structure formation and densification of Nd3+:Y3Al5O12 laser ceramics has been studied. It is shown that the use of 50- and 100-nm yttrium oxide particles makes it possible to synthesize single-phase yttrium aluminum garnet at temperatures of 1200 and 1500°C, respectively, whereas in the case of 5000-nm yttrium oxide particles 2-h exposure at a temperature of 1500°C yields only 80 wt % of the Nd3+:Y3Al5O12 phase. Bulk swelling of pressed samples during sintering of 2.94Y2O3-0.06Nd2O3-5Al2O3 powders with the size ratio of the initial particles R(Al2O3/Y2O3) ~ 5 is observed. The application of different-sized powders (R ~ 2.5) provides quantitative ratios between phases in the 3Y2O3-5Al2O3 system at which shrinkage in a temperature range of 20–1500°C is dominant. Laser ceramics 0–2 at % Nd3+:Y3Al5O12 have been obtained by the solid-phase sintering of oxide powders (R ~ 2.5). The slope efficiency for 1 at % Nd3+:Y3Al5O12 laser ceramics is found to be 33%. 相似文献
4.
Cd 1‐xSn xS thin films were successfully deposited on suitably cleaned glass substrate by chemical bath deposition method at 74 °C. Hydrated Stannous Chloride (SnCl 2.2H 2O) in aqueous solution was added to the CdS growing solution in different proportions. The experimental results indicate, a successful doping for lower concentration of Sn, saturation for intermediate doping levels, and a degradation of the doping process for higher concentration of Sn. Indirect (X‐ray diffraction) and Direct (Scanning electron microscopy) measurements were performed to characterize the growth and the nature of crystallinity of the different Cd 1‐xSn xS films. The effect of annealing on the crystal structure and morphology of the deposited films has also been discussed. The X‐ray diffraction spectra show that the thin films are polycrystalline and have both cubic and hexagonal structure. The Interplanar spacing, lattice constant, grain size, strain, and dislocation density were calculated for as‐deposited and annealed films. The grain size was found to decrease from 5 nm to 0.89 nm with doping concentration of Sn. The grain size further decreased due to annealing at 400 °C. SEM studies show layered growth and long needle like structures along with some voids. After annealing the densification and smaller size of the particles was also observed. The optical absorption spectra show shifting of absorption peaks towards lower wavelength side (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
A new kind of 5 at% Yb‐doped Lu 0.5Y 0.5PO 4 crystals were firstly grown by spontaneously nucleated high‐temperature solution method using lead pyrophosphate (Pb 2P 2O 7) as the solvent. The X‐ray powder diffraction (XRPD) patterns recorded at room temperature showed the crystals possessed tetragonal xenotime structure. The polarized absorption spectra and the fluorescence spectra of Yb:Lu xY 1‐xPO 4 were measured at room temperature, respectively. The results show that Yb:Lu xY 1‐xPO 4 mixed crystal will be a promising laser material if the crystal size and quality is further improved. 相似文献
6.
The mixed oxide (Gd 1‐xY x) 2O 3 (0.0 ≤ x ≤ 1.0) were synthesized, as powder and thin film, by a sol‐gel process. X‐ray diffraction data were collected and crystal structure and microstructure analysis were performed using Rietveld refinement method. All samples were found to have the same crystal system and formed solid solutions over the whole range of x. The cationic distribution, Gd 3+ and Y 3+, over the two non‐equivalent sites 8b and 24d of the space group Ia3 is found to be random for all values of (x). The lattice parameter is found to vary linearly with the composition (x). Replacing Gd 3+ and Y 3+ by each other introduces a systemic decrease in the x‐coordinate of cation position (24d) and slight changes in the oxygen coordinates. Crystallite size and microstrain analysis is performed along different crystallographic directions and anisotropic changes are found with the composition parameter (x). The average crystallite size ranges from 75 to 149 nm and the r.m.s strain from 0.027 to 0.068 x10 ‐2. Textured Gd 1.841Y 0.159O 3 (400) buffer layers, with a high degree of alignment in both out‐plane and in‐plan, are successfully grown on cube textured Ni (001) tape substrates by sol–gel dip coating process. The resulting buffer layers are crack‐free, pinhole‐free, dense and smooth. YbBa 2Cu 3O 7‐x (YbBCO) thin film could be (00 l) epitaxially grown on the obtained buffer layer using sol–gel dipping technique. (© 2007 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
7.
Sol-gel processing of ceramic materials for advanced applications involves several steps starting from precursor synthesis and ending up with multicomponent metal oxides. A simple sol-gel synthesis technique has been refined to prepare the precursors for the superconducting (Y 1−xSc x)Ba 2Cu 4O 8 and (Y 1−xGa x)Ba 2Cu 4O 8 compounds. The amorphous gel powders were characterized by powder X-ray diffraction, infrared spectroscopy, thermal analysis and elemental analysis. A systematic characterization of precursor gels led us to predict the approximate composition and the chemical reactions involved during gelation. The stability and high level of homogeneity obtained for the gels make them suitable as processable precursors to substituted (Y 1−xSc x)Ba 2Cu 4O 8 and (Y 1−xGa x)Ba 2Cu 4O 8 superconducting compounds. 相似文献
8.
The (CuInSe 2) x(2ZnSe) 1‐x and (CuInTe 2) x(2ZnTe) 1‐x solid solution crystals prepared by Bridgman method and chemical vapor transport have been studied. The nature of the crystalline phases, the local structure homogeneity and composition of these materials have been investigated by X‐ray diffraction (XRD) and Electron Probe Microanalysis (EPMA) methods. The analysis revealed the presence of chalcopyrite‐sphalerite phase transition between 0.6 ≤ X ≤ 0.7. Lattice constants, value of σ position parameter and bond length between atoms were also calculated. It was found that the lattice parameters exhibit a linear dependence versus composition. The transmission spectra of solid solution crystals in the region of the main absorption edge were studied. It was established that the optical band gap of these materials changes non‐linearly with the X composition. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
9.
Zirconium‐doped ceria hollow slightly‐truncated nano‐octahedrons (HTNOs) (Ce 1‐xZr xO 2) were synthesized by a one‐pot, facile hydrothermal method. The morphology and crystalline structure were characterized with powder X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and the high resolution transmission electron microscopy (HRTEM). The composition and chemical valence on the surface of the as‐prepared Ce 1‐xZr xO 2 powders were detected by X‐ray photoelectron spectroscopy (XPS) and energy dispersive spectrometry (EDS). The surface area and pore size distribution of as‐obtained Zr‐doped ceria HTNOs were measured by N 2 adsorption‐desorption measurement. Mechanisms for the growth of Zr‐doped ceria HTNOs are proposed as both oriented attachment and Ostwald ripening process and the formation of the hollow structure is strongly dependent on the addition of Zr 4+ ions. Furthermore, the as‐obtained Zr‐doped ceria HTNOs revealed superior catalytic activity and thermal stability toward CO oxidation compared to pure ceria. It may provide a new path for the fabrication of inorganic hollow structures on introducing alien metal ions. 相似文献
10.
Porous nanoplates made of yttrium orthovanadate doped with europeum (YVO 4:Eu 3+) have been successfully synthesized via a chemical co-precipitation method using NH 4VO 3, Y 2O 3, Eu 2O 3 and ethylene glycol. To investigate the effect of temperature on the pore size and morphology of the final product, the as-synthesized YVO 4:Eu 3+ nanoplates were subjected to heat treatment at 300 and 600 °C for 2 h. The obtained samples were characterized by X-ray diffractometion, Fourier-transform infrared spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy and photoluminescence spectroscopy. The experimental results showed that the luminescent properties were significantly enhanced with increasing pore size of the YVO 4:Eu 3+ porous nanoplates. 相似文献
11.
A series of synthetic garnets solid solutions is compositions between Y 3Al 2Al 3O 12 (Y-Al garnet) (YAG) and Ca 3Cr 2Si 3O 12 (uvarovite) was synthesized using the sol-gel method. The expected general formula is (Ca xY 1-x) 3 (Cr xAl 1-x) 2 (Si xAl 1-x) 3O 12 where x = 0 to x = 1. The cation distribution in dodecahedral, octahedral and tetrahedral sites and bond distances in these synthetic garnets were determined using the Rietveld method. It shows the incomplete substitution in small sites. The smaller site the smaller substitution there is. 相似文献
12.
For the first time specific heats of the face centered cubic solid solutions (Bi 2O 3) 1−x(Y 2O 3) x in the temperature range 350–1000 K were measured by means of Differential Scanning Calorimetry. Samples were also investigated with thermal expansion. The results showed the phase transitions for (Bi 2O 3) 0.75 (Y 2O 3) 0.25, which is acsribed to δ → δ* change in lattice mentioned in literature and for (Bi 2O 3) 0.58(Y 2O 3) 0.42, which is connected with a metastable behaviour of this sample. 相似文献
13.
The tetragonally double alkaline rare earth molybdates NaRe(MoO 4) 2 (Re = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, and Er) micro‐particles in aqueous solution of Re(NO 3) 3 and Na 2MoO 4 were prepared hydrothermally by a facile and effective EDTA‐assisted method, and investigated by XRD, SEM, FE‐SEM, photoluminescence (PL) excitation and emission spectra. The results showed that the radii of Re ions, pH and the molar ratio of Re(NO 3) 3/Na 2MoO 4 in the synthesis solution play an important role in controlling sizes, morphologies and luminescent properties of the final products. And the possible formation mechanism for the bipyramid‐like structure and role of EDTA were discussed in detail. The microstructure and PL property of NaY xLa 1‐x(MoO 4) 2:10%Eu 3+ was investigated, and it showed that NaY 0.5La 0.5(MoO 4) 2 exhibited regular sphere‐like morphology and emitted the stronger red emission with better color purity than other products. When Tm 3+, Dy 3+ and Eu 3+ with appropriate concentrations were used as dopants to modify this bipyramid NaY(MoO 4) 2 material, the white light emission material of NaY(MoO 4) 2:1%Tm 3+‐11%Dy 3+‐0.6%Eu 3+ was successfully synthesized and its CIE chromaticity coordinates is (0.33, 0.33), which is the standard white light point. These novel white‐light‐emitting NaY(MoO 4) 2:1%Tm 3+‐11%Dy 3+‐0.6%Eu 3+ with single phase would be a promising material in the WLED field. 相似文献
14.
Strontium‐doped lanthanum manganite (La 1‐xSr xMnO 3 or LSM) is the material most widely used on solid oxide fuel cells cathode. In this work, nano‐scale La 0.8Sr 0.2MnO 3 powders have been synthesized by polymeric precursor‐based methods using different polymerizing agents with the aim of evaluating the influence of this change in the final powder. The powders calcined at 700 °C for 2 h have been characterized by X‐ray diffraction (XRD), scanning electron microscopy (FE‐SEM) and Fourier transform infrared spectroscopy (FTIR) in order to investigate the quality of both synthesis routes. It is shown that the crystal structure and morphology of the particles are significantly dependent on the preparation conditions. Single phase and La 0.8Sr 0.2MnO 3 nano‐crystalline particles less than 30 nm were obtained using ethylene glycol as polymerizing agent. FTIR results have been indicated that only the powder obtained using gelatin presented small traces of hydroxyl groups on its surface. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
The physical and technical conditions for reproducible production of nanodispersed yttrium aluminum garnet (Y 3Al 5O 12, YAG) and yttrium oxide (Y 2O 3) powders by chemical coprecipitation have been investigated. It is established that the obtained YAG nanopowders have enhanced
reactivity, which significantly decreases the temperature range of interaction in the Y 2O 3-Al 2O 3 system in comparison with ceramic synthesis. It is shown that vacuum heat treatment may lead to reversible transformation
of the YAG crystal structure from cubic to tetragonal. 相似文献
16.
The influence of Y 2O 3 and CdO content on the phase composition, structure, and electrical properties of Y 2O 3-CdO-BaO-CuO ceramics was studied. The concentration limits of the existence of the orthorhombic perovskite-like Y xBa 2 ? x Cd yCu 1 ? y O 3 + δ solid solutions (where 0.20 ≤ x ≤ 0.37 and y ≤ 0.2) and their unit-cell parameters are determined. 相似文献
17.
A modified wet-chemical synthesis technology was put forward to fabricate Eu 3+/Dy 3+ doped with YNb xP 1−xO 4 and YNb xV 1−xO 4 phosphors with varying x from the assembly of multicomponent hybrid precursors. The morphologies have been found to be 1–2 μm crystalline spheres using XRD and SEM. The red photoluminescence intensity reaches the strongest in YNb 0.8P 0.2O 4:Eu 3+ and YNb 0.1V 0.9O 4:Eu 3+ phosphors and the red to orange intensity ratio (RO) values decrease with the content of P(V) increasing. Besides this, the optimum concentration for Dy 3+ luminescence in YNb 0.5P 0.5O 4 is 1 mol%, while that in YNb 0.5V 0.5O 4 is 0.5 mol% or lower than 0.5 mol%. The yellow to blue intensity ratio (YB) value of Dy 3+ increases when the Dy 3+ concentration increases from 0.5 to 8 mol% in YNb 0.5P 0.5O 4; however, that of Dy 3+ does not vary much in YNb 0.5V 0.5O 4 matrix. 相似文献
18.
The primary nano-crystallization of fcc Al in initially amorphous Al 85Ni 8Y 5Co 2 has been studied by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) in combination with energy electron loss spectroscopy (EELS), high-resolution transmission electron microscopy (HRTEM) and X-ray diffractometry (XRD). TEM in combination with EELS after both isochronal and isothermal annealing allowed the determination of the change of the crystalline particle density and particle density/size distribution. The crystallization in Al 85Ni 8Y 5Co 2 was found to take place in three sequences. In the first step of the first sequence spherical fcc Al nano-particles develop with a very high particle density. In the second step of the first sequence the more or less spherical Al particles develop protrusions without significant further nucleation of fcc Al particles. In the second sequence nucleation of new fcc Al particles takes place. Comparing the crystallization behavior of Al 85Ni 8Y 5Co 2 with that of Al 85Ni 5Y 8Co 2 it follows that the yttrium solute level has a strong influence on the nucleation and growth behavior during the fcc Al primary nano-crystallization. 相似文献
19.
The microhardness and fracture toughness of laser nanocrystalline ceramics based on the cubic oxides Y 2O 3 and Y 3Al 5O 12 are determined experimentally. It is shown by comparative measurements that the fracture toughness and microhardness of Y 2O 3 ceramics exceed the corresponding parameters of Y 2O 3 single crystals by factors of 2.5 and 1.3, respectively. The fine morphology of grains and grain boundaries in fractures is investigated. It is ascertained that changes in the mechanical properties of the nanocrystalline ceramics under study are related to both the sizes and structure of grains and the structure of grain boundaries. It is suggested that twinning processes determine the mechanisms of formation of nanocrystalline ceramics. 相似文献
20.
SiO 2-BaO-ZnO-xB 2O 3-(10−x) Y 2O 3, (0 ≤ x ≤ 10) glasses are synthesized. The effect of Y 2O 3 on the structural and optical properties of glasses has been investigated using different characterization techniques. The results are discussed in light of non-bridging oxygens (NBO), optical basicity and heat-treatment of glasses. The band gap has been calculated for as cast and heat-treated glasses. The band gap energy is found to decrease with the increasing content of Y 2O 3 in the glasses and heat-treatment. The presence of the crystalline phase in the glass matrix showed remarkable effect on band gap which decreases to semiconducting range. 相似文献
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