The Effect of sulfating on the Crystalline Structure of Sol-Gel Zirconia Nanophases

1996 ◽  
Vol 457 ◽  
Author(s):  
Bokhimi ◽  
A. Morales ◽  
O. Novaro ◽  
M. Portilla ◽  
T. Lopez ◽  
...  
Keyword(s):  
Crystalline Structure ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Sol Gel ◽  
Main Phase ◽  
Sulfate Ions ◽  
X Ray ◽  
Initial Stage

ABSTRACTNanophases of sol-gel zirconia were prepared with HCl, C2H4O2 and NH4OH as hydrolysis catalysts, and sulfated with H2SO4. They were analyzed by using X-ray powder diffraction, and their crystalline structure was refined by using the Rietveld method. All samples annealed below 300 °C were amorphous. The non-sulfated samples crystallized around 350 °C, while the sulfated samples crystallized around 600 °C, when they started loosing sulfate ions. In the initial stage of crystallization, both the tetragonal and monoclinic nanophases coexisted, with the tetragonal as the main phase. Annealing the samples at higher temperatures transformed the tetragonal nanophase, stabilized by OH ions, into the monoclinic one.

Crystalline Structure and Morphology of the Phases in MgO, TiO2 and ZrO2 Prepared by the Sol-Gel Technique

1995 ◽  
Vol 405 ◽  
Author(s):  
Bokhimi ◽  
J. L. Boldu ◽  
E. Muñoz ◽  
O. Novaro ◽  
T. Lopez ◽  
...  
Keyword(s):  
Crystalline Structure ◽  
Powder Diffraction ◽  
Sol Gel ◽  
Temperature Evolution ◽  
X Ray ◽  
Structure And Morphology ◽  
Gel Technique ◽  
Effect Of Doping

AbstractThe temperature evolution of the crystalline structure of the nanophases found in sol-gel MgO, TiO2 and ZrO2 systems was analyzed by performing x-ray powder diffraction. The structure and concentration of each phase was determined by using the Rietveld technique. The effect of doping MgO and TiO2 systems with platinum was also studied.

Crystallographic study of ternary ordered skutterudite IrGe1.5Se1.5

2010 ◽  
Vol 25 (3) ◽  
pp. 247-252 ◽  
Author(s):  
F. Laufek ◽  
J. Návrátil
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Crystallographic Data ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Crystallographic Study ◽  
Related Phase ◽  
The Ideal

The crystal structure of skutterudite-related phase IrGe1.5Se1.5 has been refined by the Rietveld method from laboratory X-ray powder diffraction data. Refined crystallographic data for IrGe1.5Se1.5 are a=12.0890(2) Å, c=14.8796(3) Å, V=1883.23(6) Å3, space group R3 (No. 148), Z=24, and Dc=8.87 g/cm3. Its crystal structure can be derived from the ideal skutterudite structure (CoAs3), where Se and Ge atoms are ordered in layers perpendicular to the [111] direction of the original skutterudite cell. Weak distortions of the anion and cation sublattices were also observed.

Rietveld refinement of the solid-solution series: (Cu,Mg)SO4·H2O

1995 ◽  
Vol 10 (3) ◽  
pp. 189-194 ◽  
Author(s):  
C. L. Lengauer ◽  
G. Giester
Keyword(s):  
Solid Solution ◽  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Solid Solution Series ◽  
Cation Site ◽  
Tg Analysis ◽  
X Ray ◽  
Solution Series

The kieserite-type solid-solution series of synthetic (Cu,Mg)SO4·H2O was investigated by TG-analysis and X-ray powder diffraction using the Rietveld method. Representatives with Cu≥20 mol% are triclinic distorted () analogous to the poitevinite (Cu,Fe)SO4·H2O compounds. Cation site ordering with preference of Cu for the more distorted M1 site was additionally proven by the structure refinement.

Rietveld Refinement of the BaTiO3 from X-Ray Powder Diffraction

2009 ◽  
Vol 79-82 ◽  
pp. 593-596
Author(s):  
Feng Sun ◽  
Yan Sheng Yin
Keyword(s):  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Structural Parameters ◽  
Ferroelectric Ceramic ◽  
Powder Diffraction Data ◽  
Ceramic Powders ◽  
Space Group ◽  
X Ray

The ferroelectric ceramic BaTiO3 was synthesized at 1000 °C for 5 h. The structure of the system under study was refined on the basis of X-ray powder diffraction data using the Rietveld method. The system crystallizes in the space group P4mm（99）. The refinement of instrumental and structural parameters led to reliable values for the Rp, Rwp and Rexp.We use the TOPAS software of Bruker AXS to refine this ceramic powders and show its conformation

Crystal structure of potassium tetraperoxomolybdate (VI) K2[Mo(O2)4]

2005 ◽  
Vol 20 (3) ◽  
pp. 203-206 ◽  
Author(s):  
M. Grzywa ◽  
M. Różycka ◽  
W. Łasocha
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Crystal Structure Refinement ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters

Potassium tetraperoxomolybdate (VI) K2[Mo(O2)4] was prepared, and its X-ray powder diffraction pattern was recorded at low temperature (258 K). The unit cell parameters were refined to a=10.7891(2) Å, α=64.925(3)°, space group R−3c (167), Z=6. The compound is isostructural with potassium tetraperoxotungstate (VI) K2[W(O2)4] (Stomberg, 1988). The sample of K2[Mo(O2)4] was characterized by analytical investigations, and the results of crystal structure refinement by Rietveld method are presented; final RP and RWP are 9.79% and 12.37%, respectively.

scholarly journals Structural Properties Analysis of Mg-β-TCP by X-ray Powder Diffraction with the Rietveld Refinement

2020 ◽  
Vol 9 (4) ◽  
pp. 1562-1568
Keyword(s):  
Powder Diffraction ◽  
Rietveld Method ◽  
Quantitative Phase Analysis ◽  
Structural Refinement ◽  
Osteoporosis Therapy ◽  
X Ray ◽  
Cell Parameters ◽  
Biomineralization Process ◽  
Resultant Powder ◽  
Rapid Reaction

The incorporation of magnesium in the synthetic apatite has been associated with the biomineralization process and osteoporosis therapy in humans and animals. β-tricalcium phosphate (β-TCP) is one of the most common bioceramics widely applied in bone cement and implants. In this work, Ca-deficient apatite (CDA) with a theoretical 0.08 Mg/(Ca+Mg) ratio was synthesized by the rapid reaction between Ca(OH)2, MgCl2.6H2O and H3PO4 at 40°C and the resultant powder calcined at 650 °C for 10h. X-ray powder diffraction analysis (XRD), in combination with the Rietveld method (Fullprof-suite), was employed for quantitative phase analysis and structural refinement. The results of XRD indicate that magnesium can substitute for calcium into a β-TCP structure inducing a reduction of the cell parameters and the compound crystallizes in the rhombohedral R3c structure, with the following unit cell constants: a = b = 10.3560 Å, c = 37.1718 Å, and cell volume V = 3452.44. The analysis indicated that the substitution of Mg2+ on the M(4) and M(5) sites were, approximately, 2.61 and 6.97 mol%, corresponding to the Ca2.72(MgIV0.07, MgV0.21)(PO4)2 stoichiometric formula and 0.09 Mg/(Ca+Mg) ratio.

Structure Refinements of the Layered Intergrowth Phases SbIIISbV x A 1−x TiO6 (x≃0, A = Ta, Nb) Using Synchrotron X-ray Powder Diffraction Data

1997 ◽  
Vol 53 (6) ◽  
pp. 861-869 ◽  
Author(s):  
C. D. Ling ◽  
J. G. Thompson ◽  
S. Schmid ◽  
D. J. Cookson ◽  
R. L. Withers
Keyword(s):  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Homologous Series ◽  
Rietveld Method ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Synchrotron Source ◽  
X Ray ◽  
The Family

The structures of the layered intergrowth phases SbIIISb^{\rm V}_xAl-xTiO6 (x \simeq 0, A = Ta, Nb) have been refined by the Rietveld method, using X-ray diffraction data obtained using a synchrotron source. The starting models for these structures were derived from those of Sb^{\rm III}_3Sb^{\rm V}_xA 3−xTiO14 (x = 1.26, A = Ta and x = 0.89, A = Nb), previously solved by single-crystal X-ray diffraction. There were no significant differences between the derived models and the final structures, validating the approach used to obtain the models and confirming that the n = 1 and n = 3 members of the family, Sb^{\rm III}_nSb^{\rm V}_xA n−xTiO4n+2 are part of a structurally homologous series.

Laboratory X-ray powder diffraction: a comparison of different geometries with special attention to the usage of the CuKα doublet

1999 ◽  
Vol 32 (4) ◽  
pp. 799-807 ◽  
Author(s):  
Martin Oetzel ◽  
Gernot Heger
Keyword(s):  
Powder Diffraction ◽  
Profile Analysis ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Strong Dependence ◽  
Line Profile Analysis ◽  
X Ray ◽  
Diffraction Angle ◽  
Maximum Parameters ◽  
The Right

In a laboratory X-ray powder diffraction study, the evaluation of the patterns of three Bragg–Brentano powder diffractometers with different monochromator geometries has been undertaken. For the measurements on each diffractometer, the standard reference material SRM 640 (silicon) and the corundum samples SRM 674a and SRM 1976 have been used. In each case, the peak profiles were fitted with a split Pearson VII function and the FWHM (full width at half-maximum) parameters and exponentmwere determined for the left (lower 2θ) and the right (higher 2θ) sides of the Bragg peaks. It was found that there is a strong dependence of both the FWHM and the exponentmon the diffraction angle for the two configurations that included monochromators, whereas nearly constant values ofmwere found for the geometrically simplest diffractometer working without a monochromator. Finally, the two components of the CuKα doublet show systematically different peak profiles. There is a clear difference not only concerning the FWHM, which becomes more obvious at higher 2θ values, but also in the course ofmwith respect to the diffraction angle for the left and the right tails of the powder reflections. This is the main reason for the difficulties inKα2stripping and also in single-line-profile analysis when using theKα doublet. Therefore, it is not surprising that this phenomenon, which can be explained by Heisenberg's uncertainty principle, does affect the reliability (represented by standardRvalues) of structure refinement by the Rietveld method.

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