scholarly journals Structural determination of new solid solutions [Y2-xMx][Sn2-xMx]o7-3x/2 (M = Mg or Zn) by Rietveld method

2010 ◽  
Vol 4 (4) ◽  
pp. 237-243 ◽  
Author(s):  
Mohamed Douma ◽  
Hossain El ◽  
Raquel Trujillano ◽  
Vicente Rives
Keyword(s):  
Solid Solutions ◽  
Rietveld Method ◽  
Structural Parameters ◽  
Pyrochlore Structure ◽  
Solid State Reaction Method ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Pyrochlore Type ◽  
Ft Ir

New [Y2-xMx][Sn2-xMx]O7-3x/2 (0 ?x? 0.30 for M = Mg and 0 ?x? 0.36 for M = Zn) solid solutions with the pyrochlore structure were synthesized via high-temperature solid-state reaction method. Powder X-ray diffraction (PXRD) patterns and Fourier transform infrared (FT-IR) spectra showed that these materials are new non-stoichiometric solid solutions with the pyrochlore type structure. The structural parameters for the solids obtained were successfully determined by Rietveld refinement based on the analysis of the PXRD diagrams. Lattice parameter (a) of these solid solutions decreases when x increases in both series. All samples obtained have the pyrochlore structure Fd-3m, no. 227 (origin at center -3m) with M2+ (M = Mg2+ or Zn2+) cations in Y3+ and Sn4+ sites, thus creating vacancies in the anionic sublattice.

scholarly journals Ion-exchange properties of solid solutions based on hydrated forms of monovalent metals antimonate-tungstates

2020 ◽  
Vol 62 (6) ◽  
pp. 74-79
Author(s):  
Olga A. Firsova ◽  
◽  
Elena M. Filonenko ◽  
Yulia A. Lupitskaya ◽  
Hurshid N. Bozorov ◽  
...  
Keyword(s):  
Ir Spectroscopy ◽  
Ion Exchange ◽  
Solid Solutions ◽  
Rietveld Method ◽  
Type Structure ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pyrochlore Type ◽  
Exchange Properties

The research of tungsten-antimony crystalline acid (TACA) structural transformations in the condition of ion-exchange and thermolysis of its substituted M+, H+-forms (M+ – Li, Na, K, Ag) were conducted. The data of thermogravimetric and qualitative X-ray phase analyses made it possible to conclude that the thermolysis of TACA and its derivatives proceeds in a wide temperature range from 300 to 1150 K being accompanied by the removal of crystalline water molecules with the formation of phases mixture containing complex antimony oxides of the ( -,  - Sb2O4) modification and WO3. It was shown that compounds based on hydrated forms of monovalent metal antimonates-tungstates are stable up to 1023 K with a pyrochlore-type structure. For pyrochlore-like phases, a monotonic dependence of unit cell parameter a on ion-exchange degree α and the ionic radius of metals r was revealed indicating the formation of solid solutions Мх(Н3О)1–хWSbO6 nН2О (M+ – Li, Na, K, Ag; 0.0≤х<1.0; 0.0≤n<2.0) with a limited range of solubility from the crystal chemistry point of view. Within the framework of the Fd-3m space group, based on the data of X-ray diffraction analysis (Rietveld method), the structural characteristics of TACA and its substituted M+, H+-forms were refined, and a model for populating the corresponding metal ions by crystallographic positions of the pyrochlore-type structure was proposed. Using a complex of physicochemical methods (thermogravimetric, X-ray diffraction analyses and IR spectroscopy), a correlation between the composition of the obtained compounds, structural disorder, and ion-exchange properties were determined. According to the data of thermogravimetry and IR spectroscopy, it follows that the degree of compounds hydration analyzed depends on the nature of the alkaline ion. This allows to conclude that lithium and sodium ions are located in 16d– positions, dragging neutral water molecules into the structure occupying 8b-positions. In this case, potassium ions can partially occupy both 16d- and 8b-positions of the structure.

X-ray structure determination of the rare earth oxides (Er1−uGdu)2O3applying the Rietveld method

2002 ◽  
Vol 35 (5) ◽  
pp. 577-580 ◽  
Author(s):  
Zein Heiba ◽  
Hasan Okuyucu ◽  
Y. S. Hascicek
Keyword(s):  
Rare Earth ◽  
Rietveld Method ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gel Technique ◽  
Average Size

Nanosized polycrystalline samples of (Er1−uGdu)2O3(0 ≤u≤ 1.0) were synthesized by a sol–gel technique. X-ray diffraction data were collected and the crystal structures were refined by the Rietveld method. All samples are found to have the same crystal system and formed solid solutions over the whole range ofu. The Er3+and Gd3+ions were randomly distributed over two cationic sites, 8band 24d, in the space groupIa\bar{3} (206) in all refined structures. The lattice parameter was found to vary non-linearly with the composition (u). The average microstrain and average crystallite size have been calculated from the Williamson–Hall plots for each sample. The average size ranges from 50 to 70 nm, and the microstrain from 0.4 to 1.7%.

scholarly journals Structural Analysis of Interstratified Illite-Smectite by the Rietveld Method

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 244
Author(s):  
Xiaoli Wang ◽  
Hejing Wang
Keyword(s):  
Structural Information ◽  
Rietveld Method ◽  
Structural Parameters ◽  
Structural Parameter ◽  
X Ray Diffraction ◽  
Recursive Structure ◽  
X Ray ◽  
Powder Samples ◽  
Xrd Patterns

Rietveld method is a powerful tool in obtaining structural information of clay minerals by using of X-ray diffraction (XRD) patterns. However, the interstratified illite-smectites (I-S) show various stacking defects preventing the direct application of this method. It was shown that the Rietveld method combined with a recursive structure-factor calculation can be used for describing the stacking disorder of I-S. In this study, a series of samples with different stacking sequences and different proportions of layer types were chosen to verify the applicability of Rietveld method in determination of structural parameters of I-S. The Rietveld refinements were carried out on powder samples and oriented specimens in air-dry (AD) and ethylene glycol (EG) state. The structural information obtained by X-ray fluorescence (XRF) and thermal analysis were used as an independent test of the reliability of the refinements. The refined and experimental results were compared systematically and the relationship between structural parameter was discussed. For powder and oriented specimens, the refined results of occupancies of potassium and iron and the proportion of illitic layers showed consistent results. The refined value of cis-vacant layers was in good agreement with the experimental data. The reliability of the refinements increased with increasing proportion of illitic layers.

scholarly journals Determination of 4-nitrophenol using MoO3 loaded glassy carbon electrode via electrochemical sensing approach

2021 ◽  
Author(s):  
Bhagyashri Kamble ◽  
Kalyanrao M. Garadkar ◽  
Kirankumar K. Sharma ◽  
Pravin Kamble ◽  
Shivaji Tayade ◽  
...  
Keyword(s):  
Glassy Carbon Electrode ◽  
Glassy Carbon ◽  
Structural Parameters ◽  
Differential Pulse ◽  
Electrochemical Sensing ◽  
Carbon Electrode ◽  
X Ray Diffraction ◽  
Hydrothermal Route ◽  
Ft Ir

In order to raise possible ways of MoO3 synthesis and improve its existing applications, MoO3 nanomaterial was successfully synthesized through the solvo-hydrothermal route by utilizing a mixture of ionic liquid (1-butyl-3-methylimidazolium bromide) as a solvent, and water as co-solvent in 1:1 ratio. The morphology and structural parameters of IL-as­sisted MoO3 product were examined by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). Additionally, the surface wettability and particle size distribution were inspected using the contact angle and dynamic light scattering (DLS) analysis. Glassy carbon electrode (GCE) surface was then modified by IL-assisted MoO3. The formed IL-MoO3/GCE was employed as an electro­chemical sensor for determination of 4-nitrophenol (4-NP), which is very toxic and important pollutant. The redox behavior of 4-NP at the surface of IL-MoO3/GCE was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Limits of detection (LOD) and limits of quantification (LOQ) determined from CV were found to be 6.76 and 22.5 mM, while from DPV recordings, 5.41 and 18.0 mM are found. The obtained results clearly reveal possible application of MoO3 for selective and sensitive sensing of 4-NP. The decorated electrode was successfully employed for determination of 4-NP in the river water real samples.

scholarly journals Ba5(IO6)2: crystal structure evolution from room temperature to 80 K

2021 ◽  
Vol 77 (6) ◽  
pp. 634-637
Author(s):  
David Wenhua Bi ◽  
Priya Ranjan Baral ◽  
Arnaud Magrez
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Structural Transition ◽  
Rietveld Method ◽  
Structural Parameters ◽  
Structure Evolution ◽  
X Ray Diffraction ◽  
Lattice Contraction ◽  
Interatomic Distances ◽  
Crystallographic Axes

The crystal structure of Ba5(IO6)2, pentabarium bis(orthoperiodate), has been re-investigated at room temperature based on single-crystal X-ray diffraction data. In comparison with a previous crystal structure determination by the Rietveld method, an improved precision of the structural parameters was achieved. Additionally, low-temperature measurements allowed the crystal structure evolution to be studied down to 80 K. No evidence of structural transition was found even at the lowest temperature. Upon cooling, the lattice contraction is more pronounced along the b axis. This contraction is found to be inhomogeneous along different crystallographic axes. The interatomic distances between different Ba atoms reduce drastically with lowering temperature, resulting in a closer packing around the IO6 octahedra, which remain largely unaffected.

SIZE-INDUCED EFFECTS IN NANOSTRUCTURED NiFe2O4

2010 ◽  
Vol 24 (30) ◽  
pp. 5973-5985
Author(s):  
M. GUNES ◽  
H. GENCER ◽  
T. IZGI ◽  
V. S. KOLAT ◽  
S. ATALAY
Keyword(s):  
Electron Microscopy ◽  
Annealing Temperature ◽  
Structural Parameters ◽  
Hydrothermal Process ◽  
Lattice Parameter ◽  
Effect Of Temperature ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

NiFe 2 O 4 nanoparticles were successfully prepared by a hydrothermal process, and the effect of temperature on them was studied. The particles were annealed at various temperatures ranging from 413 to 1473 K. Studies were carried out using powder X-ray diffraction, scanning electron microscopy, infrared spectroscopy, differential thermal analysis, thermogravimetric analysis and a vibrating sample magnetometer. The annealing temperature had a significant effect on the magnetic and structural parameters, such as the crystallite size, lattice parameter, magnetization and coercivity.

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