Pyrochlores. VII. The Oxides of Antimony: an X-Ray and Mössbauer Study

1972 ◽  
Vol 50 (5) ◽  
pp. 690-700 ◽  
Author(s):  
David J. Stewart ◽  
Osvald Knop ◽  
Conrad Ayasse ◽  
F. W. D. Woodhams
Keyword(s):  
Type A ◽  
Mössbauer Study ◽  
Simultaneous Reduction ◽  
X Ray ◽  
Density Determination ◽  
Pyrochlore Type ◽  
Cubic Structure ◽  
Antimonic Acid ◽  
Mössbauer Parameters ◽  
Defect Pyrochlore

Antimonic acid cannot be dehydrated by heating in air to give products of constant and reproducible weight without simultaneous reduction of some of the SbV to SbIII. Neither anhydrous Sb2O5 nor the hydroxy oxide Sb3O6OH postulated by Dihlström and Westgren can be obtained by this method. Two well-defined products of the dehydration/decomposition are Sb2O4.35(5) = Sb6O13, which forms between 650 and 850°, and β-Sb2O4. The latter, and not Sb2O3, results on heating Sb6O13 to 935°. Sb6O13 has a cubic structure of the defect pyrochlore type, a0 = 10.303(1) Å, x(O2) = 0.4304(14). Combined evidence from X-ray diffractometry, density determination, and Mössbauer spectroscopy leads to Sb3+Sb5+2O6O0.5 as the most probable structural formula.The Mössbauer parameters of β-Sb2O4 are closely similar to those reported for α-Sb2O4, but the isomer shifts (relative to InSb at 77°K) for SbV in antimonic acid and Sb6O13 are significantly larger than those in α- and β-Sb2O4.

MÖSSBAUER STUDY OF Mg0.9Mn0.1CryFe2-yO4 SPINEL FERRITES

2006 ◽  
Vol 20 (07) ◽  
pp. 365-372 ◽  
Author(s):  
A. LAKSHMAN ◽  
P. S. V. SUBBA RAO ◽  
K. H. RAO
Keyword(s):  
Magnetic Field ◽  
Room Temperature ◽  
Single Phase ◽  
Field Model ◽  
Hyperfine Magnetic Field ◽  
Trivalent Chromium ◽  
X Ray Diffraction ◽  
Mössbauer Study ◽  
X Ray ◽  
Mössbauer Parameters

The effect of the substitution of paramagnetic trivalent chromium ions in stoichiometric magnesium–manganese ferrites has been studied with the composition Mg 0.9 Mn 0.1 Cr y Fe 2-y O 4 where y varies from 0.0, 0.1 to 0.9 in steps of 0.2. The single-phase cubic spinel structure of these samples has been confirmed from X-ray diffraction analyses. Mössbauer spectra of these samples studied at room temperature (300 K) showed two characteristic ferrimagnetic Zeeman sextets for lower concentration of Cr 3+ followed by relaxation phenomenon corresponding to y=0.9. The dependence of Mössbauer parameters, viz. isomer shift, quadrupole splitting, line width and hyperfine magnetic field on Cr 3+ concentration have been discussed. The variation of hyperfine magnetic field with increasing Cr 3+ content has been explained on the basis of Neel's molecular field model.

Study of Natural Minerals of U-Ryrochlore-Type Structure as Analogues of Plutonium Ceramic Waste-form

2002 ◽  
Vol 713 ◽  
Author(s):  
Roman V. Bogdanov ◽  
Yuri F. Batrakov ◽  
Elena V. Puchkova ◽  
Andrey S. Sergeev ◽  
Boris E. Burakov
Keyword(s):  
Chemical Shifts ◽  
Pyrochlore Structure ◽  
Type Structure ◽  
Waste Form ◽  
X Ray ◽  
Ceramic Waste ◽  
Natural Minerals ◽  
The Us ◽  
Pyrochlore Type

ABSTRACTAt present, crystalline ceramic based on titanate pyrochlore, (Ca,Gd,Hf,Pu,U)2Ti2O7, is considered as the US candidate waste form for the immobilization of weapons grade plutonium. Naturally occuring U-bearing minerals with pyrochlore-type structure: hatchettolite, betafite, and ellsworthite, were studied in orders to understand long-term radiation damage effects in Pu ceramic waste forms. Chemical shifts (δ) of U(Lδ1)– and U(Lβ1) – X-ray emission lines were measured by X-ray spectrometry. Calculations were performed on the basis of a two-dimensional δLá1- and δLδ1- correlation diagram. It was shown that 100% of uranium in hatchettolite and, probably, 95-100% of uranium in betafite are in the form of (UO2)2+. formal calculation shows that in ellsworthite only 20% of uranium is in the form of U4+ and 80% of the rest is in the forms of U5+ and U6+. The conversion of the initial U4+ ion originally occurring in the pyrochlore structure of natural minerals to (UO2)2+ due to metamict decay causes a significant increase in uranium mobility.

scholarly journals The influence of exocyclic lone pairs on the bonding and geometry of type A mesoionic rings

2021 ◽  
Author(s):  
Christopher Antony Ramsden ◽  
Wojciech Piotr Oziminski
Keyword(s):  
Ab Initio ◽  
Type A ◽  
Nbo Analysis ◽  
Ring Systems ◽  
X Ray ◽  
X Ray Crystallography ◽  
Bond Model ◽  
Lone Pairs ◽  
Mp2 Calculations ◽  
Good Agreement

AbstractBased on structures determined by X-ray crystallography, ab initio MP2 calculations on type A mesoionic rings give geometries in good agreement with observed values. A study of four mesoionic ring systems, each with exocyclic oxygen, nitrogen or carbon groups, shows that the presence and configuration of exocyclic lone pairs significantly influences the geometry and configurational preference. Using a localised bond model and NBO analysis, these effects are rationalised in terms of an anomeric interaction of lone pairs with the antibonding orbitals of adjacent σ bonds. In agreement with experiment, similar effects are calculated for pyran-2-imines.

X-ray and Mössbauer study of rapidly solidified Ce20Fe80 ribbons; effect of the quenching rate

1994 ◽  
Vol 88 (1) ◽  
pp. 65-71 ◽  
Author(s):  
G. Roulin ◽  
J. Teillet ◽  
A. Fnidiki ◽  
B. Labulle ◽  
P. Ochin
Keyword(s):  
Mössbauer Study ◽  
Quenching Rate ◽  
X Ray ◽  
Rapidly Solidified

A 19F, 119Sn nuclear magnetic resonance and 119Sn Mössbauer study of the SnF2–MF–H2O system

1984 ◽  
Vol 62 (3) ◽  
pp. 591-595 ◽  
Author(s):  
Thomas Birchall ◽  
Georges Dénès
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Spectroscopic Data ◽  
Dominant Species ◽  
Mössbauer Study ◽  
Frozen Solution ◽  
Nmr Data ◽  
Mössbauer Measurements ◽  
Mössbauer Parameters ◽  
High Concentrations ◽  
Frozen Solutions

19F and 119Sn nmr spectroscopy has been used to study the SnF2–MF–H2O (M = Li+, Na+, K+, Rb+, Cs+, and [NH4]+) system. The nmr data have been supplemented by frozen solution 119Sn Mössbauer measurements. The evidence suggests that the dominant species in the SnF2–H2O system is a hydrated stannous fluoride, probably SnF2•H2O having Mössbauer parameters of δ = 3.46 mm s−1 and Δ = 1.70 mm s−1. When F− is added to these solutions rapid F− exchange occurs with the hydrated SnF2 and the dominant species becomes [SnF3]−. The 119Sn nmr chemical shift of [SnF3]− is ~ −700 ppm from (CH3)4Sn. The 119Sn Mössbauer parameters for frozen solutions of [SnF3]− are δ = ~ 3.1 mm s−1 Δ = 1.9 mm s−1. These spectroscopic data are cation dependent. We could find no strong evidence for high concentrations of [Sn2F5]− in any of these solutions.

Surface structure, nanocrystallite and defects in (ZrTi)CN nanocomposite irradiated by electron beam

2021 ◽  
pp. 2150111
Author(s):  
M. Yu. Tashmetov ◽  
I. I. Yuldashova ◽  
N. B. Ismatov
Keyword(s):  
Electron Beam ◽  
Surface Structure ◽  
Electron Beam Irradiation ◽  
Rietveld Method ◽  
Nanocomposite Coating ◽  
Beam Irradiation ◽  
X Ray ◽  
Nanocrystallite Size ◽  
Atomic Force ◽  
Cubic Structure

Effect of 2 MeV electron beam at the current density 0.09 nA/cm2 on surface structure, nanocrystallite size of (ZrTi)CN nanocomposite coating on steel was investigated at Scanning Electron and Atomic Force microscopes, and also X-ray diffractometer. Using the Rietveld method, two structure phases were indentified in the pristine samples: (ZrTi)(CN)-cubic (space group Fm-3m) and TiC — trigonal (sp.gr.R-3m). Electron beam irradiation to the fluency of [Formula: see text] electron/cm2 resulted in the phase transition of TiC from trigonal (sp.gr.R-3m) to cubic structure (sp.gr.Fm-3m). Besides, nanocrystallite size and shape have changed after the fluency [Formula: see text] electron/cm2. The lattice parameters have increased up to [Formula: see text] electron/cm2 fluence and the nanorcrystallite size of nanocomposite was enlarged 26%, which was attributed to generation of defects.

scholarly journals Mössbauer study of Fe phases in terrestrial olivine basalts from southern Egypt

Mineralogia ◽  
2013 ◽  
Vol 44 (1-2) ◽  
pp. 3-12 ◽  
Author(s):  
Kamaleldin M. Hassan ◽  
Julius Dekan
Keyword(s):  
Optical Microscopy ◽  
Crystal Chemistry ◽  
Mössbauer Spectra ◽  
Mossbauer Spectroscopy ◽  
X Ray Diffraction ◽  
Mössbauer Study ◽  
Hyperfine Parameters ◽  
X Ray ◽  
Mossbauer Spectra ◽  
Oxidized Iron

AbstractOlivine basalts from southern Egypt were studied by 57Fe Mössbauer spectroscopy at 297 and 77 K, and by optical microscopy and X-ray diffraction. The 57Fe Mössbauer spectra show three-magnetic sextets, three doublets of ferrous (Fe2+), and a weak ferric (Fe3+) doublet that is attributable to a nanophase oxide (npOx). The magnetic sextets relate to titanomagnetite and the Fe2+ doublets to olivine, pyroxene, and ulvöspinel. Variations in the hyperfine parameters of the various Fe components are attributed to changes in the local crystal chemistry. The intensity of oxidation (Fe3+/ΣFe) in the rocks varies from 20-27% with the oxidized iron largely residing in the titanomagnetite.

scholarly journals Synthesis, Characterization, and NH3 Sensing Properties of (Zn0.7 Mn0.3-x Cex Fe2O4) Nano-Ferrite

2021 ◽  
Vol 2114 (1) ◽  
pp. 012040
Author(s):  
Laith Saheb ◽  
Tagreed M. Al-Saadi
Keyword(s):  
Recovery Time ◽  
Particle Distribution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sensing Properties ◽  
Auto Combustion ◽  
Cubic Structure ◽  
Sensing Characteristics ◽  
Combustion Technique ◽  
Higher Sensitivity

Abstract This study includes the preparation of novel nano ferrite (Zn0.7 Mn0.3-x Cex Fe2O4) by using the auto combustion technique. For the following molar values, the percentage x was calculated: 0.0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3. The nano-ferrite was calcined for 2 hours at 500°C. The energy dispersive x-ray spectroscopy (EDX), X-ray diffraction (XRD) and field emission scanning electron microscopy FE-SEM was used to examine structural, morphological, and sensing properties. The spinel cubic structure was revealed by XRD findings. The particle distribution was shown to contain voids by FE-SEM. The testing of sensing characteristics to NH3 gas indicated that the synthesized nano-ferrite has a small response time ranging from (15.3-25.2) s as well as a small recovery time between (36-58.5) s, also has a higher sensitivity of about 72.23%.

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