scholarly journals Cr doped ZnO nanostructures: synthesis, electronic structures, and magnetic properties

2017 ◽  
Vol 95 (11) ◽  
pp. 1225-1232 ◽  
Author(s):  
Michael W. Murphy ◽  
William R. Diebel ◽  
Yun-Mui Yiu ◽  
Tsun-Kong Sham
Keyword(s):  
Dopant Concentration ◽  
Magnetic Measurements ◽  
Tetrahedral Site ◽  
Sol Gel ◽  
Secondary Phase ◽  
Processing Temperature ◽  
X Ray ◽  
Zno Nanostructure ◽  
Cr Concentration ◽  
X Ray Absorption

In this experiment, we have attempted to dope Cr into ZnO nanostructure as a function of dopant concentration using sol-gel method, followed by controlled thermal annealing with some success. We have also examined the samples thus prepared with scanning electron microscopy (SEM), X-ray powder diffraction (XRD), near edge X-ray absorption fine structure (NEXAFS), both theoretical and experimental, and magnetic measurements. We found that low concentration of Cr can indeed be doped in ZnO and is substitutional, occupying the tetrahedral site. However, upon increasing dopant concentration and annealing temperature, a secondary phase with Cr occupying an octahedral site precipitates out, which was evident from SEM, XRD, and NEXAFS. Ferromagnetism at room temperature was not observed in any samples, although at low Cr concentration and 400 °C processing temperature, antiferromagnetism can be seen; however, at higher concentrations or processing temperatures, the samples show only paramagnetism.

Application of In Situ X-ray Absorption Spectroscopy to Study Dilute Chromium Ions in a Molten Chloride Salt

2019 ◽  
Author(s):  
Jisue Moon ◽  
Carter Abney ◽  
Dmitriy Dolzhnikov ◽  
James M. Kurley ◽  
Kevin A. Beyer ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Local Structure ◽  
Chloride Salt ◽  
X Ray ◽  
Molten Chloride ◽  
Stable Species ◽  
Higher Temperature ◽  
Cr Concentration ◽  
X Ray Absorption

The local structure of dilute CrCl<sub>3</sub> in a molten MgCl<sub>2</sub>:KCl salt was investigated by <i>in situ</i> x-ray absorption spectroscopy (XAS) at temperatures from room temperature to 800<sup>o</sup>C. This constitutes the first experiment where dilute Cr speciation is explored in a molten chloride salt, ostensibly due to the compounding challenges arising from a low Cr concentration in a matrix of heavy absorbers at extreme temperatures. CrCl<sub>3</sub> was confirmed to be the stable species between 200 and 500<sup>o</sup>C, while mobility of metal ions at higher temperature (>700<sup>o</sup>C) prevented confirmation of the local structure.

scholarly journals The Study of Magnetic Properties for Non-Magnetic Ions Doped BiFeO3

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4061
Author(s):  
Yongtao Li ◽  
Liqing Liu ◽  
Dehao Wang ◽  
Hongguang Zhang ◽  
Xuemin He ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Local Structure ◽  
Metal Ion ◽  
Single Phase ◽  
Sol Gel ◽  
X Ray ◽  
Co Doping ◽  
Magnetic Ions ◽  
X Ray Absorption ◽  
Fe Ions

BiFeO3 is considered as a single phase multiferroic. However, its magnetism is very weak. We study the magnetic properties of BiFeO3 by Cu and (Cu, Zn). Polycrystalline samples Bi(Fe0.95Cu0.05)O3 and BiFe0.95(Zn0.025Cu0.025)O3 are prepared by the sol-gel method. The magnetic properties of BiFe0.95(Zn0.025Cu0.025)O3 are greater than that of BiFeO3 and Bi(Fe0.95Cu0.05)O3. The analyses of X-ray absorption fine structure data show that the doped Cu atoms well occupy the sites of the Fe atoms. X-ray absorption near edge spectra data confirm that the valence state of Fe ions does not change. Cu and Zn metal ion co-doping has no impact on the local structure of the Fe and Bi atoms. The modification of magnetism by doping Zn can be understood by the view of the occupation site of non-magnetically active Zn2+.

CuOX Films for NO2 Detection: Microstructural Characterization

2013 ◽  
Vol 481 ◽  
pp. 133-136 ◽  
Author(s):  
T.N. Myasoedova ◽  
G.E. Yalovega ◽  
N.K. Plugotarenko ◽  
M. Brzhezinskaya ◽  
V.V. Petrov ◽  
...  
Keyword(s):  
Gas Sensors ◽  
Secondary Electron ◽  
Operating Temperature ◽  
Sol Gel ◽  
Microstructural Characterization ◽  
Temperature Treatment ◽  
Copper Oxides ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

Copper oxides films as promising materials for gas sensors applications were studied. Copper oxide films were deposited onto Si/SiO2substrates using a citrate sol-gel method with the subsequent temperature treatment at 150-5000C. These films were characterized by means of secondary electron microscopy (SEM) and X-ray-absorption near-edge structure (XANES) spectroscopy. The prepared films were utilized in NO2sensors. The dependences of the NO2response on the operating temperature and NO2concentration (10-200 ppm) were investigated. The maximum NO2response was achieved for the film annealed at 2500C.

Magnetic Properties of Bulk Zn0.95-XMnXFe0.05O2 Prepared by Sol-Gel Method and Subsequent Hot Pressing

2011 ◽  
Vol 268-270 ◽  
pp. 356-359 ◽  
Author(s):  
Wen Song Lin ◽  
C. H. Wen ◽  
Liang He
Keyword(s):  
Magnetic Properties ◽  
Photoelectron Spectroscopy ◽  
Raw Materials ◽  
Sol Gel ◽  
Secondary Phase ◽  
X Ray Diffraction ◽  
Gel Method ◽  
X Ray ◽  
Sol Gel Method ◽  
Doped Zno

Mn, Fe doped ZnO powders (Zn0.95-xMnxFe0.05O2, x≤0.05) were synthesized by an ameliorated sol-gel method, using Zn(CH3COO)2, Mn(CH3COO)2and FeCl2as the raw materials, with the addition of vitamin C as a kind of chemical reducer. The resulting powder was subsequently compacted under pressure of 10 MPa at the temperature of 873K in vacuum. The crystal structure and magnetic properties of Zn0.95-xMnxFe0.05O2powder and bulk samples have been investigated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). X-ray photoelectron spectroscopy (XPS) was used to study chemical valence of manganese, iron and zinc in the samples. The x-ray diffraction (XRD) results showed that Zn0.95-xMnxFe0.05O (x≤0.05) samples were single phase with the ZnO-like wurtzite structure. No secondary phase was found in the XRD spectrum. X-ray photoelectron spectroscopy (XPS) showed that Fe and Mn existed in Zn0.95-xMnxFe0.05O2samples in Fe2+and Mn2+states. The results of VSM experiment proved the room temperature ferromagnetic properties (RTFP) of Mn, Fe co-doped ZnO samples.

X-ray absorption and XPS study of titanium mixed oxides synthesized by the sol–gel method

2001 ◽  
Vol 114-116 ◽  
pp. 307-311 ◽  
Author(s):  
José E. Gonçalves ◽  
Sandra C. Castro ◽  
Aline Y. Ramos ◽  
Maria C.M. Alves ◽  
Yoshitaka Gushikem
Keyword(s):  
Mixed Oxides ◽  
Sol Gel ◽  
Gel Method ◽  
X Ray ◽  
Sol Gel Method ◽  
Xps Study ◽  
X Ray Absorption

scholarly journals Structural Evolution in Wet Mechanically Alloyed Co-Fe-(Ta,W)-B Alloys

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 800
Author(s):  
Vladimír Girman ◽  
Maksym Lisnichuk ◽  
Daria Yudina ◽  
Miloš Matvija ◽  
Pavol Sovák ◽  
...  
Keyword(s):  
Structural Changes ◽  
Magnetic Measurements ◽  
Structural Evolution ◽  
High Energy ◽  
Control Agent ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
Transmission Electron ◽  
X Ray Absorption

In the present study, the effect of wet mechanical alloying (MA) on the glass-forming ability (GFA) of Co43Fe20X5.5B31.5 (X = Ta, W) alloys was studied. The structural evolution during MA was investigated using high-energy X-ray diffraction, X-ray absorption spectroscopy, high-resolution transmission electron microscopy and magnetic measurements. Pair distribution function and extended X-ray absorption fine structure spectroscopy were used to characterize local atomic structure at various stages of MA. Besides structural changes, the magnetic properties of both compositions were investigated employing a vibrating sample magnetometer and thermomagnetic measurements. It was shown that using hexane as a process control agent during wet MA resulted in the formation of fully amorphous Co-Fe-Ta-B powder material at a shorter milling time (100 h) as compared to dry MA. It has also been shown that substituting Ta with W effectively suppresses GFA. After 100 h of MA of Co-Fe-W-B mixture, a nanocomposite material consisting of amorphous and nanocrystalline bcc-W phase was synthesized.

Effects of Lattice Defects on Cathode Properties of LiMn2O4 Synthesized at Low Temperatures for Lithium Ion Secondary Battery

2008 ◽  
Vol 388 ◽  
pp. 41-44 ◽  
Author(s):  
Hiroyuki Kaiya ◽  
Shinya Suzuki ◽  
Masaru Miyayama
Keyword(s):  
Absorption Spectroscopy ◽  
Low Temperatures ◽  
Heating Temperature ◽  
Sol Gel ◽  
Lithium Ion ◽  
Lattice Defects ◽  
X Ray ◽  
Secondary Battery ◽  
Cation Mixing ◽  
X Ray Absorption

Effects of lattice defects on cathode properties of LiMn2O4 synthesized at low temperatures were investigated. LiMn2O4 powders were synthesized by a sol-gel method. The specific capacities of LiMn2O4 decreased from 134 to 81 mAh g-1 with decreasing heating temperature from 750 to 200°C. X-ray absorption spectroscopy showed that a large amount of lattice defects such as cation vacancies existed and cation mixing occurred in LiMn2O4 calcined at low temperatures. It was found that the low specific capacities of LiMn2O4 calcined at low temperatures were attributed to these lattice defects.

scholarly journals Manganese incorporation in synthetic hercynite

2015 ◽  
Vol 79 (3) ◽  
pp. 635-647 ◽  
Author(s):  
G. D. Bromiley ◽  
G. D. Gatta ◽  
T. Stokes
Keyword(s):  
Single Crystal ◽  
Absorption Spectroscopy ◽  
Structure Refinement ◽  
Tetrahedral Site ◽  
Silicate Melt ◽  
X Ray ◽  
Octahedral Sites ◽  
Partial Disorder ◽  
X Ray Absorption ◽  
Preferential Incorporation

AbstractManganese incorporation in synthetic hercynite, and partitioning between hercynite and silicate melt synthesized at 1.0 GPa, 1250°C, and at an fO2 buffered by Fe–FeO, has been studied by X-ray absorption spectroscopy and single-crystal X-ray structure refinement. Spectra indicate the presence of both Mn2+ and Mn3+ (and possibly also Mn4+) in synthetic hercynite and partitioning of Mn2+ into the melt phase, and Mn3+ into hercynite, respectively, under run conditions. X-ray refinement is consistent with partial disorder of Fe and Al across tetrahedral and octahedral sites. A higher than expected degree of Fe-Al disorder in the Mn-bearing hercynite can be explained by preferential incorporation of Mn2+ onto the tetrahedral site, and indicates that Fe-Al disorder in pure, stoichiometric hercynite cannot necessarily be used to determine closure temperatures in natural spinel. However, partitioning of Mn2+ and Mn3+ between melt and hercynite suggests that Mn incorporation in hercynite could be used as a measure of fO2 conditions in magmas during spinel crystallization.

scholarly journals The Atomic-Scale Interaction of Bioactive Glasses with Simulated Body Fluid

2005 ◽  
Vol 480-481 ◽  
pp. 21-26 ◽  
Author(s):  
L.J. Skipper ◽  
F.E. Sowrey ◽  
D.M. Pickup ◽  
R.J. Newport ◽  
K.O. Drake ◽  
...  
Keyword(s):  
Simulated Body Fluid ◽  
Body Fluid ◽  
Sol Gel ◽  
Atomic Scale ◽  
X Ray Diffraction ◽  
Bioactive Glasses ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

The formation of a carbonate-containing hydroxyapatite, HCAp, layer on bioactive calcium silicate sol-gel glass of the formula (CaO)0.3(SiO2)0.7 has been studied in-vitro in Simulated Body Fluid (SBF). Extended X-ray Absorption Fine Structure (EXAFS), X-ray Absorption Near Edge Structure (XANES), X-ray diffraction (XRD), and solid state nuclear magnetic resonance (NMR) measurements have been performed with results showing the formation of a significantly amorphous HCAp layer after less than 5 hours in solution.

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