scholarly journals Crystallization Process and Site-Selective Excitation of Nd3+ in LaF3/NaLaF4 Sol–Gel-Synthesized Transparent Glass-Ceramics

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 464
Author(s):  
María E. Cruz ◽  
Jing Li ◽  
Giulio Gorni ◽  
Alicia Durán ◽  
Glenn C. Mather ◽  
...  
Keyword(s):  
Crystallization Process ◽  
Sol Gel ◽  
Glass Ceramics ◽  
X Ray Diffraction ◽  
Oxyfluoride Glass ◽  
Excitation Spectra ◽  
Molar Ratios ◽  
Transmission Electron ◽  
Site Selective ◽  
First Time

In this study, transparent oxyfluoride glass-ceramics (GCs) with NaLaF4 nanocrystals (NCs) were prepared by the sol–gel method for the first time. Three different molar ratios of La(CH3COO)3/Na(CH3COO) were used to obtain the GCs, which were sintered at 450, 550 and 650 °C for 1 min. X-ray diffraction (XRD) was employed to follow the evolution of the xerogel during the heat treatments and to study crystal growth for the three temperatures. In all cases, the LaF3 crystalline phase was present, but crystallization of NaLaF4 was only promoted at 650 °C. Thermogravimetric and thermodifferential analysis (TGA-DTA) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the crystallization process. High-resolution transmission electron microscopy (HRTEM) was employed to confirm NaLaF4 crystallization and determine the size distribution. The incorporation of Nd3+ ion into NaLaF4 and LaF3 nanocrystals was confirmed by site-selective emission and excitation spectra. The Nd3+ emission intensities in both phases depend not only on the NaLaF4/LaF3 ratio but also on their emission efficiencies.

Effects of Glass Elements on the Structural Evolution ofin situGrown Ferroelectric Perovskite Crystals in Sol-gel Derived Glass-ceramics

1997 ◽  
Vol 12 (4) ◽  
pp. 1131-1140 ◽  
Author(s):  
Kui Yao ◽  
Weiguang Zhu ◽  
Liangying Zhang ◽  
Xi Yao
Keyword(s):  
Crystallization Process ◽  
Sol Gel ◽  
Glass Ceramics ◽  
Structural Evolution ◽  
Dielectric Measurements ◽  
X Ray Diffraction ◽  
Process Change ◽  
X Ray ◽  
Ferroelectric Perovskite

Several ABO3perovskite ferroelectric crystals, PbTiO3, Pb(Zr, Ti)O3, and BaTiO3have beenin situgrown from amorphous gels with glass elements, and the structural evolution has been systematically investigated using x-ray diffraction (XRD), infrared spectra (IR), differential thermal analysis (DTA), thermogravimetric analysis (TGA), and dielectric measurements. It is found that in the Si-contained glass-ceramic systems, Si and B glass elements are incorporated into the crystalline structures, resulting in the variation of the crystallization process, change of lattice constant, and dielectric properties. Some metastable phases expressed by a general formula AxByGzOw(A = Pb and Ba; B = Zr and Ti; G for glass elements, especially for Si) have been observed and discussed.

Upconversion Luminescence Properties of NaYF4 Nanocrystals Precipitated Nd3+/Yb3+/Ho3+ Tri-Doped Oxyfluoride Glass Ceramics

2016 ◽  
Vol 16 (4) ◽  
pp. 3744-3748 ◽  
Author(s):  
Yuan Gao ◽  
Yuebo Hu ◽  
Dacheng Zhou ◽  
Jianbei Qiu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Energy Transfer Process ◽  
Upconversion Luminescence ◽  
Glass Ceramics ◽  
X Ray Diffraction ◽  
Oxyfluoride Glass ◽  
X Ray ◽  
Transmission Electron ◽  
The Matrix

Transparent oxyflouride glass ceramics composed of SiO2–Al2O3–Na2O–NaF–YF3 tri-coped with Nd3+/Yb3+/Ho3+ were prepared by thermal treatment. Segregation of NaYF4 nanocrystals in the matrix was confirmed from structural analysis by means of X-ray diffraction and transmission electron microscopy. Compared with glass samples, very strong green upconversion (UC) luminescence due to the Ho3+:(4F5, 5S2)→5I8 transition was observed in the glass ceramics under 808 nm excitation. It was found that upconversion intensity of Ho3+ strongly depends on the Nd3+ concentration, and the energy transfer process from Nd3+ to Ho3+ via Yb3+ was proposed.

Microstructural characteristics and photoluminescence performance of nanograined thermally treated CeO2-TiO2 xerogels

2007 ◽  
Vol 22 (5) ◽  
pp. 1182-1187
Author(s):  
Amita Verma ◽  
A.K. Srivastava ◽  
N. Karar ◽  
Harish Chander ◽  
S.A. Agnihotry
Keyword(s):  
Electron Microscopy ◽  
Crystallite Size ◽  
Sol Gel ◽  
Structural Features ◽  
X Ray Diffraction ◽  
Molar Ratios ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Crystallite Sizes ◽  
Thermally Treated

Nanostructured thermally treated xerogels have been synthesized using a sol-gel process involving cerium (Ce) chloride heptahydrate and titanium (Ti) propoxide mixed in different Ce:Ti molar ratios. Structural features of the xerogels have been correlated with their photoluminescence (PL) response. The crystallite sizes in the samples lie in the nanorange. The x-ray diffraction and transmission electron microscopy results have confirmed the coexistence of CeO2 and TiO2 nanocrystallites in these xerogels. In general, a decrease in the CeO2 crystallite size and an increase in the TiO2 crystallite size are observed in the xerogels as a function of Ti content. Scanning electron microscopy results have evidenced the evolution of ordered structure in the xerogels as a function of TiO2 content. Although both of the phases (CeO2 and TiO2) have exhibited PL in ultraviolet and visible regions, the major luminescence contribution has been made by the CeO2 phase. The largest sized CeO2 crystallites in 1:1 thermally treated xerogel have led to its highest PL response. PL emission in the xerogels is assigned to their nanocrystalline nature and oxygen vacancy-related defects.

Sol–gel synthesis, structural and electrical properties of Li2CoSiO4 cathode material

2014 ◽  
Vol 07 (06) ◽  
pp. 1440001 ◽  
Author(s):  
Michał Świętosławski ◽  
Marcin Molenda ◽  
Piotr Natkański ◽  
Piotr Kuśtrowski ◽  
Roman Dziembaj ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Sol Gel ◽  
Lithium Ion ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Structural And Electrical Properties ◽  
Potential Alternative ◽  
Sol Gel Synthesis ◽  
First Time

Polyanionic cathode materials for lithium-ion batteries start to be considered as potential alternative for layered oxide materials. Among them, Li 2 CoSiO 4, characterized by outstanding capacity and working voltage, seems to be an interesting substitute for LiFePO 4 and related systems. In this work, structural and electrical investigations of Li 2 CoSiO 4 obtained by sol–gel synthesis were presented. Thermal decomposition of gel precursor was studied using EGA (FTIR)-TGA method. Chemical composition of the obtained material was confirmed using X-ray diffraction and energy-dispersive X-ray spectroscopy. The morphology of β- Li 2 CoSiO 4 was studied using transmission electron microscopy. High temperature electrical conductivity of Li 2 CoSiO 4 was measured for the first time. Activation energies of the electrical conductivity of two Li 2 CoSiO 4 polymorphs (β and γ) were determined. The room temperature electrical conductivity of those materials was estimated as well.

Silver Doped Nano-Sized Bioglass Ceramics: Synthesis, Characterization and Biocompatibility Studies

2016 ◽  
Vol 860 ◽  
pp. 25-28 ◽  
Author(s):  
Chinnasamy Ramaraj Mariappan ◽  
Narender Ranga
Keyword(s):  
Sol Gel ◽  
Glass Ceramics ◽  
X Ray Diffraction ◽  
Bending Vibrations ◽  
Tem Analysis ◽  
Transmission Electron ◽  
Visible Spectra ◽  
Calcium Phosphosilicate ◽  
Uv Visible

We report on the structural and biocompatibility properties of nanosized calcium phosphosilicate bioglass ceramics doped with 0, 2, 4 and 6 mol% Ag2O. Silver doped bioceramics were synthesized by sol-gel method. The prepared samples were characterized by means of powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-visible and high resolution transmission electron microscopy. The XRD reveals the glass-ceramic nature of the samples. The FT-IR spectra show the possible stretching and bending vibrations of silicate and phosphate groups. Absorptions in UV-visible spectra reveal the silver embedment as Ag+/Ago form into the glass matrix. nanosize of the glass ceramics is confirmed by HR-TEM analysis. The bioactivity of silver doped bioceramics was investigated by in-vitro method with Dulbecco’s Modified Eagel’s Medium. It confirms the formation of bone-like hydroxylapatite layer formation on the surface of bioceramics.

Functionalized Silicate Supported TiO2-ZnO Nanocomposite Film and its Application in Simultaneous Photocatalytic Degradation of Toxic Molecules

2013 ◽  
Vol 764 ◽  
pp. 255-265 ◽  
Author(s):  
R. Dhanalakshmi ◽  
A. Pandikumar ◽  
R. Ramaraj
Keyword(s):  
Electron Microscopy ◽  
Sol Gel ◽  
Xrd Analysis ◽  
Potential Candidate ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
Chemical Route ◽  
Molar Ratios ◽  
Amine Functionalized ◽  
Transmission Electron

The TiO2-ZnO nanocomposite materials ((TiO2-ZnO)NCM) with different molar ratios (Ti:Zn) was synthesized by chemical route and dispersed in functionalized silicate sol-gel matrix (Silicate/(TiO2-ZnO)NCM)). The as prepared Silicate/(TiO2-ZnO)NCM were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The dispersion of the small amount of (TiO2-ZnO)NCM in silicate sol-gel matrix paves the way for the preparation of solid-state thin film photocatalyst which is advantageous for the separation of the catalyst from solution, the substrates and the reaction products. The simultaneous photoinduced oxidation of methylene blue (MB) dye and reduction of Cr (VI) to Cr (III) was examined at different amine functionalized silicate sol-gel embedded (TiO2-ZnO)NCM films. The (TiO2-ZnO)NCM dispersed into the amine functionalized silicate sol-gel matrix (TPDT) exhibited enhanced photocatalytic activity when compared to the (TiO2-ZnO)NCM without the silicate sol-gel. The functionalized silicate sol-gel supported (TiO2-ZnO)NCM is a potential candidate for energy conversion and environment remediation and cleaning applications.

Effect of TiO2 addition on the preparation of β-spodumene powders by sol-gel process

1999 ◽  
Vol 14 (1) ◽  
pp. 196-203 ◽  
Author(s):  
Moo-Chin Wang ◽  
Ming-Hong Lin ◽  
Hok-Shing Liu
Keyword(s):  
Electron Microscopy ◽  
Ph Value ◽  
Sol Gel ◽  
Gelation Time ◽  
Glass Ceramics ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Fine Glass ◽  
A Minor

This study has shown the possibility of achieving two primary considerations for the advanced fabrication of spodumene with a composition of Li2O · Al2O3 · 4SiO2 · nTiO2 (LAST) glass-ceramics by a sol-gel process, namely, an enormous reduction of sintering temperature from 1600 to 1200 °C together with the appearance of simple phases of β-spodumene/rutile as opposed to products via the conventional melting-crystallization process. Fine glass-ceramic powders with a composition of Li2O · Al2O3 · 4SiO2 (LAS) have been synthesized by the sol-gel process using Si(OC2H5)4, Al(OC2H5)3, LiOCH3, and Ti(OC2H5)4 as the starting materials. The process included well-controlled hydrolysis polycondensation of the raw alkoxides. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron diffraction (ED) analysis were utilized to study the effect of TiO2 addition on the preparation of β-spodumene powders by the sol-gel process. The gelation time of the LAST solution increases as the TiO2 content increases. For the low (<3) or high (>11) pH value, the gelation time was shortened. At pH = 5, regardless of the TiO2 content, the gel has the longest time of gelation. When the dried gels of the LAST system are heated from 800 to 1200 °C, the crystallized samples are composed of the major phase of β-spodumene and a minor phase of rutile (TiO2).

Preparation of TiO2/Ga2O3 Nanowires by a Sol-Gel-Solvothermal Method

2010 ◽  
Vol 663-665 ◽  
pp. 965-968
Author(s):  
Yue Hui Wang ◽  
Dong Jun Wang ◽  
Ai Jun Song ◽  
Zhi Gang Zhang ◽  
Shi Tao Song
Keyword(s):  
Electron Microscopy ◽  
Near Infrared ◽  
Solvothermal Method ◽  
Sol Gel ◽  
Nitrogen Adsorption ◽  
Tetrabutyl Titanate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
First Time

TiO2/Ga2O3 nanowires were successfully prepared by a sol–gel-solvothermal method using tetrabutyl titanate as precursor, alcohol as solvent, Ga2O3 as templet and dopants, alginate as dispersant. The structures, morphologies,compositions and catalytic activity of products have been characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy ( FESEM ), nitrogen adsorption test, ultraviolet-visible near-infrared spectroscopy (UV–vis–NIR ),energy dispersive X-ray (EDX) analysis and spectrophotometer. The results revealed that the as-synthesized TiO2/Ga2O3 nanowires grew along [001] direction,which is reported for the first time, and the as-prepared product had better optical activity than TiO2 nanoparticles. Finally, the nanowires have a good adsorption capacity of 128.2 m2/g tested through nitrogen adsorption.

Nucleation efficiency of erbium and ytterbium fluorides in transparent oxyfluoride glass-ceramics

2005 ◽  
Vol 20 (2) ◽  
pp. 472-481 ◽  
Author(s):  
G. Dantelle ◽  
M. Mortier ◽  
D. Vivien ◽  
G. Patriarche
Keyword(s):  
Cell Parameter ◽  
Glass Ceramics ◽  
Parameter Study ◽  
X Ray Diffraction ◽  
Oxyfluoride Glass ◽  
X Ray ◽  
Oxyfluoride Glasses ◽  
Transmission Electron ◽  
Optical Applications ◽  
Co Doped

Oxyfluoride glasses (GeO2–PbO–PbF2) doped with erbium and/or ytterbium fluorides were prepared. Highly transparent glass-ceramics, containing β–PbF2 nanocrystallites, were successfully obtained by controlled glass devitrification and were studied as they could lead to promising optical applications. To characterize the samples, differential thermal analysis, x-ray diffraction, and transmission electron microscopy were performed, revealing a variation of the crystallites size, the crystallites number and β–PbF2 crystallization temperature according to the doping ion. Indeed, the analyses indicated differences between erbium and ytterbium fluorides in promoting the crystallization of the fluoride phase. Although both fluorides act as seeds for β–PbF2 heterogeneous nucleation, erbium fluoride has higher nucleation efficiency than ytterbium fluoride and runs the nucleation process in co-doped samples. Energy dispersive x-ray microanalysis insured high rare-earth segregation into the crystallites, proving the formation of a solid solution Pb1−x−yErxYbyF2 +x+y, also confirmed by the unit cell parameter study.

scholarly journals Synthesis of ZnO-CuO Nanocomposite Aerogels by the Sol-Gel Route

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Rula M. Allaf ◽  
Louisa J. Hope-Weeks
Keyword(s):  
Electron Microscopy ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Copper Nitrate ◽  
Zinc Hydroxide ◽  
X Ray Diffraction ◽  
Molar Ratios ◽  
Transmission Electron ◽  
Composite Aerogels ◽  
Copper Composite

The epoxide addition sol-gel method has been utilized to synthesize porous zinc-copper composite aerogels in the zinc-to-copper molar ratios of 50 : 50 to 90 : 10. A two-step mixing approach has been employed to produce aerogels composed of nano- to micrometer sized particles. The aerogels were characterized by ultrahigh resolution scanning electron microscopy, transmission electron microscopy, and powder X-ray diffraction. The as-synthesized aerogels had a thin flake- or petal-like microstructure comprised of clustered flakes on two size scales; they were identified as being crystalline with the crystalline species identified as copper nitrate hydroxide, zinc hydroxide chloride hydrate, and zinc hydroxide nitrate hydrate. Annealing of the aerogel materials at a relatively low temperature (400°C) resulted in a complete phase transition of the material to give highly crystalline ZnO-CuO aerogels; the aerogels consisted of networked nanoparticles in the ~25–550 nm size range with an average crystallite size of ~3 nm and average crystallinity of 98%. ZnO-CuO aerogels are of particular interest due to their particular catalytic and sensing properties. This work emphasizes the versatility of this sol-gel route in synthesizing aerogels; this method offers a possible route for the fabrication of aerogels of different metal oxides and their composites.

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