OPTIMIZATION OF HEAT TREATMENTS OF AFRICAN GREEN SAPPHIRES

2001 ◽  
Vol 15 (20) ◽  
pp. 873-882 ◽  
Author(s):  
P. WINOTAI ◽  
S. SAISENG ◽  
T. SUDYOADSUK
Keyword(s):  
Emission Spectra ◽  
High Ratio ◽  
Hexagonal Structure ◽  
Blue Color ◽  
Green Color ◽  
X Ray ◽  
Bluish Green ◽  
Spin Resonance ◽  
Maximum Decrease ◽  
Golden Color

Under suitable heating conditions designed for a particular sapphire it is possible to change the color in order to increase its value. It was found that heating African green sapphires in an oxygen atmosphere could improve their quality and thus increase their prices. The color of green sapphires is due to the presence of trace amounts of Fe 3+, Ni 3+, Fe 2+ and Ti 4+ ions. It is known that Fe 3+ yields pale yellow and Ni 3+ a golden color while the charge transfer mechanism between Fe 2+ and Ti 4+ gives sapphire its blue color. It is obvious that the green color is due to a high ratio of Fe 2+ to Ti 4+. By using an X-ray diffractometer, the maximum decrease of the c/a ratio of the hexagonal structure is found to occur after heat treatment at 1200°C. These results are also confirmed by the shift of emission spectra toward shorter wavelengths. Furthermore, the number of Fe 2+ ions converted to Fe 3+ was detected by electron spin resonance spectrometry and found to increase with temperature. The sapphire with trace Ti 4+ ions, appeared slightly bluish green after heating at 1500°C. The optimal temperature is therefore at 1300°C, where we can achieve yellowish green sapphires instead.

HEAT TREATMENTS OF TANZANIA RUBY AS MONITORED BY ESR SPECTROSCOPY

2000 ◽  
Vol 14 (16) ◽  
pp. 1693-1700 ◽  
Author(s):  
P. WINOTAI ◽  
T. WICHAN ◽  
I. M. TANG ◽  
J. YAOKULBODE
Keyword(s):  
Heat Treatment ◽  
Heat Treating ◽  
Hexagonal Structure ◽  
Blue Color ◽  
Spin Resonance ◽  
Gas Atmosphere ◽  
Two Factors ◽  
Maximum Decrease ◽  
Electron Spin Resonance Spectrometer

The main purpose of heat treatment is to find the optimum condition to either enchance or reduce the color in order to increase value of ruby. It was found that by heating a slightly bluish Tanzania ruby in oxygen gas atmosphere could lead to a more perfect ruby. While X-ray diffractometer found the maximum decrease in c/a ratio of the hexagonal structure after the heat treatment at 1200°C, the number of Fe 2+ ions converted to Fe 3+ was detected by electron spin resonance spectrometer and found to increase with heating temperatures. These were clearly two factors that reduced blue color in the Tanzania ruby. The best heat treating temperature to enhance the quality of the ruby was at 1300°C.

Synthesis and Luminescence Properties of Ba3Y1-xEuxB3O9 (0.05≤x≤0.35) under UV Excitation

2014 ◽  
Vol 906 ◽  
pp. 60-65 ◽  
Author(s):  
Xiao Xia Li
Keyword(s):  
Particle Size ◽  
Single Phase ◽  
Charge Transfer Band ◽  
Emission Spectra ◽  
Hexagonal Structure ◽  
Luminescence Properties ◽  
Excitation Energies ◽  
Excitation Spectra ◽  
X Ray ◽  
Uv Excitation

Single phase of Ba3Y1-xEuxB3O9 (0.05 ≤ x≤ 0.35)samples was prepared by the solid state reaction. The crystal structure, the surface, the particle size and luminescence properties were characterized by X-ray diffractometer, scanning electron microscopy and spectrophotometer. The results showed that the obtained samples with the particle size from 0.3 to 1.5 um were hexagonal structure. Monitored by 592 nm emission, the excitation spectra of Ba3Y1-xEuxB3O9were dominated by the charge transfer band of O2-→Eu3+ peaking at about 259 nm until x= 0.15; the transition from 7F0 to 5L6 level of Eu3+ at about 395 nm was maximum after x> 0.15. The strongest emission peak due to the 5D0→7F1transition of Eu3+ was all located at about 592 nm in the emission spectra of Ba3Y1-xEuxB3O9, and the maximum emission was obtained at x= 0.15 and 0.3 under 254 and 395 nm excitation, respectively. The excitationprocess under the two excitation energies was analyzed. It indicated that only the centrosymmetric lattices could be excited under 254 nm excitation; both the centrosymmetric and noncentrosymmetric positions could be excited by 395 nm, accordingly, the ratio of the red emission (5D0→7F2) to the orange one (5D0→7F1) increased, leading to a better chromaticity of the phosphors.

Nano-probe x-ray analysis and high-resolution imaging on planar defects in high-pressure synthesized infinite-layer superconductor

1994 ◽  
Vol 52 ◽  
pp. 728-729
Author(s):  
Y. Y. Wang ◽  
H. Zhang ◽  
V. P. Dravid ◽  
H. Zhang ◽  
L. D. Marks ◽  
...  
Keyword(s):  
High Pressure ◽  
High Resolution ◽  
Atomic Structure ◽  
Emission Spectra ◽  
High Resolution Electron Microscopy ◽  
Planar Defects ◽  
X Ray ◽  
Infinite Layer ◽  
Resolution Electron ◽  
Resolution Imaging

Azuma et al. observed planar defects in a high pressure synthesized infinitelayer compound (i.e. ACuO2 (A=cation)), which exhibits superconductivity at ~110 K. It was proposed that the defects are cation deficient and that the superconductivity in this material is related to the planar defects. In this report, we present quantitative analysis of the planar defects utilizing nanometer probe xray microanalysis, high resolution electron microscopy, and image simulation to determine the chemical composition and atomic structure of the planar defects. We propose an atomic structure model for the planar defects.Infinite-layer samples with the nominal chemical formula, (Sr1-xCax)yCuO2 (x=0.3; y=0.9,1.0,1.1), were prepared using solid state synthesized low pressure forms of (Sr1-xCax)CuO2 with additions of CuO or (Sr1-xCax)2CuO3, followed by a high pressure treatment.Quantitative x-ray microanalysis, with a 1 nm probe, was performed using a cold field emission gun TEM (Hitachi HF-2000) equipped with an Oxford Pentafet thin-window x-ray detector. The probe was positioned on the planar defects, which has a 0.74 nm width, and x-ray emission spectra from the defects were compared with those obtained from vicinity regions.

Self-Consistent Field Calculations of X-Ray Emission Spectra of Surface Adsorbates and Polymers

1997 ◽  
Vol 7 (C2) ◽  
pp. C2-515-C2-516
Author(s):  
H. Agren ◽  
L. G.M. Pettersson ◽  
V. Carravetta ◽  
Y. Luo ◽  
L. Yang ◽  
...  
Keyword(s):  
Emission Spectra ◽  
X Ray ◽  
Consistent Field ◽  
Self Consistent ◽  
Surface Adsorbates ◽  
Self Consistent Field

EXPERIMENTAL AND THEORETICAL SOFT X-RAY EMISSION SPECTRA OF Cu-Pd SUBSTITUTIONAL ALLOYS

1987 ◽  
Vol 48 (C9) ◽  
pp. C9-1059-C9-1062
Author(s):  
P. J. DURHAM ◽  
C. F. HAGUE ◽  
J.-M. MARIOT ◽  
W. M. TEMMERMAN
Keyword(s):  
Emission Spectra ◽  
X Ray ◽  
Substitutional Alloys

New Structure of CTAB Templated Silica Films as revealed by GISAXS coupled to HRTEM

2000 ◽  
Vol 628 ◽  
Author(s):  
Sophie Besson ◽  
Catherine Jacquiod ◽  
Thierry Gacoin ◽  
André Naudon ◽  
Christian Ricolleau ◽  
...  
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Grazing Incidence ◽  
Hexagonal Structure ◽  
X Ray Diffraction ◽  
Electronic Microscopy ◽  
Silica Films ◽  
X Ray ◽  
X Ray Scattering ◽  
Hexagonal Arrangement ◽  
Spherical Micelles

ABSTRACTA microstructural study on surfactant templated silica films is performed by coupling traditional X-Ray Diffraction (XRD) and Transmission Electronic Microscopy (TEM) to Grazing Incidence Small Angle X-Ray Scattering (GISAXS). By this method it is shown that spin-coating of silicate solutions with cationic surfactant cetyltrimethylammonium bromide (CTAB) as a templating agent provides 3D hexagonal structure (space group P63/mmc) that is no longer compatible with the often described hexagonal arrangement of tubular micelles but rather with an hexagonal arrangement of spherical micelles. The extent of the hexagonal ordering and the texture can be optimized in films by varying the composition of the solution.

scholarly journals Effects in the Optical and Structural Properties Caused by Mg or Zn Doping of GaN Films Grown via Radio-Frequency Magnetron Sputtering Using Laboratory-Prepared Targets

2021 ◽  
Vol 11 (15) ◽  
pp. 6990
Author(s):  
Erick Gastellóu ◽  
Godofredo García ◽  
Ana María Herrera ◽  
Crisoforo Morales ◽  
Rafael García ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Magnetron Sputtering ◽  
Radio Frequency ◽  
Hexagonal Structure ◽  
Binding Energies ◽  
Radio Frequency Magnetron ◽  
Radio Frequency Magnetron Sputtering ◽  
X Ray ◽  
Diffraction Patterns ◽  
Mg Doped

GaN films doped with Mg or Zn were obtained via radio-frequency magnetron sputtering on silicon substrates at room temperature and used laboratory-prepared targets with Mg-doped or Zn-doped GaN powders. X-ray diffraction patterns showed broadening peaks, which could have been related to the appearance of nano-crystallites with an average of 7 nm. Scanning electron microscopy and transmission electron microscopy showed good adherence to silicon non-native substrate, as well as homogeneity, with a grain size average of 0.14 µm, and 0.16 µm for the GaN films doped with Zn or Mg, respectively. X-ray photo-electron spectroscopy demonstrated the presence of a very small amount of magnesium (2.10 mol%), and zinc (1.15 mol%) with binding energies of 1303.18, and 1024.76 eV, respectively. Photoluminescence spectrum for the Zn-doped GaN films had an emission range from 2.89 to 3.0 eV (429.23–413.50 nm), while Mg-doped GaN films had an energy emission in a blue-violet band with a range from 2.80 to 3.16 eV (443.03–392.56 nm). Raman spectra showed the classical vibration modes A1(TO), E1(TO), and E2(High) for the hexagonal structure of GaN.

Photoluminescence Enhancement of CdS Nanocrystals Fabricated on Dithiocarbamate Functionalized PET Substrates

2012 ◽  
Vol 512-515 ◽  
pp. 1511-1515
Author(s):  
Chun Lin Zhao ◽  
Li Xing ◽  
Xiao Hong Liang ◽  
Jun Hui Xiang ◽  
Fu Shi Zhang ◽  
...  
Keyword(s):  
Room Temperature ◽  
Hexagonal Structure ◽  
Diffraction Measurement ◽  
X Ray Diffraction ◽  
Visible Absorption ◽  
X Ray ◽  
Cds Nanocrystals ◽  
Morphological Studies ◽  
Transmission Electron

Cadmium sulfide (CdS) nanocrystals (NCs) were self-assembled and in-situ immobilized on the dithiocarbamate (DTCs)-functionalized polyethylene glycol terephthalate (PET) substrates between the organic (carbon disulfide diffused in n-hexane) –aqueous (ethylenediamine and Cd2+ dissolved in water) interface at room temperature. Powder X-ray diffraction measurement revealed the hexagonal structure of CdS nanocrystals. Morphological studies performed by scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM) showed the island-like structure of CdS nanocrystals on PET substrates, as well as energy-dispersive X-ray spectroscopy (EDS) confirmed the stoichiometries of CdS nanocrystals. The optical properties of DTCs modified CdS nanocrystals were thoroughly investigated by ultraviolet-visible absorption spectroscopy (UV-vis) and fluorescence spectroscopy. The as-prepared DTCs present intrinsic hydrophobicity and strong affinity for CdS nanocrystals.

scholarly journals Y3+ substituted Sr-hexaferrites: sol-gel synthesis, structural, magnetic and electrical characterization

Cerâmica ◽  
2019 ◽  
Vol 65 (374) ◽  
pp. 274-281 ◽  
Author(s):  
S. S. Satpute ◽  
S. R. Wadgane ◽  
S. R. Kadam ◽  
D. R. Mane ◽  
R. H. Kadam
Keyword(s):  
Electron Microscopy ◽  
Sol Gel ◽  
Electrical Characterization ◽  
Combustion Method ◽  
Hexagonal Structure ◽  
Strontium Hexaferrite ◽  
X Ray Diffraction ◽  
X Ray ◽  
Morphological Studies ◽  
Auto Combustion

Abstract Y3+ substituted strontium hexaferrites having chemical composition SrYxFe12-xO19 (x= 0.0, 0.5, 1.0, 1.5) were successfully synthesized by sol-gel auto-combustion method. The structural and morphological studies of prepared samples were investigated by using X-ray diffraction technique, energy dispersive X-ray spectroscopy, field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy. The X-ray diffraction pattern confirmed the single-phase hexagonal structure of yttrium substituted strontium ferrite and the lattice parameters a and c increased with the substitution of Y3+ ions. The crystallite size also varied with x content from 60 to 80 nm. The morphology was studied by FE-SEM, and the grain size of nanoparticles ranged from 44 to 130 nm. The magnetic properties were investigated by using vibrating sample magnetometer. The value of saturation magnetization decreased from 49.60 to 35.40 emu/g. The dielectric constant decreased non-linearly whereas the electrical dc resistivity increased with the yttrium concentration in strontium hexaferrite.

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