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1.
    
The structure of the semiconducting alloy Cu2Cd0.5Mn0.5GeSe4 was refined from an X‐ray powder diffraction pattern using the Rietveld method. The present alloy crystallizes in the wurtz‐stannite structure, space group Pmn21 (No 31), and unit cell parameters values of a = 8.0253(2) Å, b = 6.8591(2) Å, c = 6.5734(2) Å and V = 361.84(2) Å3. The structure exhibits a three‐dimensional arrangement of slightly distorted CuSe4, Cd(Mn)Se4 and GeSe4 tetrahedras connected by corners. © 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim  相似文献   

2.
    
The crystal structure of the chalcogenide compounds CuFeAlSe3 and CuFeGaSe3, belonging to the system I‐II‐III‐III3, were characterized using X‐ray powder diffraction data. Both compounds crystallize in the tetragonal space group P42c (N° 112), Z = 1, with unit cell parameters a = 5.609(1) Å, c = 10.963(2) Å for CuFeAlSe3 and a = 5.6165(3) Å, c = 11.075(1) Å for CuFeGaSe3. These compounds are isostructural with CuFeInSe3, and have a normal adamantane structure. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

3.
    
Single crystals of the magnetic semiconductor CoIn0.5Cr1.5S4, belong to the system CoIn(2‐2X)Cr(2X)S4 with x = 0.75, was grown by the chemical transport method. X‐ray powder diffraction characterization by the Rietveld method indicated that CoIn0.5Cr1.5S4 crystallizes in the space group Fd‐3m, Z = 8, with a = 10.0700(6) Å and V = 1021.2(1) Å3, in a normal spinel structure. The temperature dependence of the DC magnetization suggests that the studied compound presents a ferromagnetic behavior with a Curie temperature Tc = 220 K. Sharp spin‐glass like behavior was found also. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

4.
    
X‐ray powder technique was used in the investigation of AgCd2GaS4–'AgZn2GaS4' section to determine the region of AgCd2GaS4‐based solubility. It was established that the solid solution forms up to 75 mol.% 'AgZn2GaS4'. The refinement of AgCd0.5Zn1.5GaS4 structure was performed. This alloy crystallizes in orthorhombic structure (space group Pmn21 ) with unit cell parameters a =0.78772(2), b =0.67221(2), c =0.64019(2) nm, V =0.33899(3) nm3. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

5.
    
Rietveld refinements of corundum, a rutile and anatase nanocrystalline synthetic mixture, and gypsum, on laboratory energy dispersive X‐ray diffraction (EDXD) data are reported. Cell parameters, positional and displacement parameters are in reasonable agreement with single‐crystal reference data, despite the rather poor resolution of EDXD data. In particular, good results were obtained for gypsum (unrestrained refinement) with counting times as short as 1000 s.  相似文献   

6.
    
The influence of the Cu‐content in the quaternary compounds CuxAg1‐xInTe2 (0 ≤ x ≤1) on the structural properties of the bulk material was discussed. Bulk ingot materials of CuxAg1‐xInTe2 solid solutions (x = 0.0, 0.25, 0.50, 0.75 and 1.0) have been synthesized by fusion of the constituent elements in the stoichiometric ratios in vacuum‐sealed silica tubes. The materials compositions were confirmed by using energy dispersive analysis of X‐rays (EDAX). X‐ray powder diffraction measurements were performed for all the prepared samples at 300 K in step scanning mode. The analysis of X‐ray data has indicated that the crystal structure of the prepared materials with different compositions is single‐phase polycrystalline materials corresponding to the tetragonal chalcopyrite structure with space group I 2d. The crystal structural parameters were refined by Rietveld method using the Full Prof program. The refined lattice constants (a and c), anion positional parameter, u, and the determined bond distances and angles were found to vary with composition, x, attaining zero tetragonal distortion at x ≈ 0.75, which corresponds to an ideal tetragonal unit cell. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

7.
    
Extended X‐ray absorption fine structure (EXAFS) and neutron scattering data from monoclinic zirconia are analysed independently and simultaneously by reverse Monte Carlo (RMC) modelling. X‐ray and neutron powder diffraction data are analysed by Rietveld refinement. The results are compared with respect to the local structure around the zirconium cations. Monoclinic zirconia was chosen as a model system for the comparison of structural information obtained by EXAFS spectroscopy and scattering methods because it is crystalline but also has some local disorder. In the case of zirconia, analysis of EXAFS spectra by RMC modelling results in reliable and accurate information on the local structure, consistent with neutron scattering and diffraction experiments.  相似文献   

8.
    
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9.
    
The ternary compound Cu2SnTe3 crystallizes in the Imm2 (Nº 44) space group, Z = 2, with a = 12.833(4) Å, b = 4.274(1) Å, c = 6.043(1) Å, V = 331.5(1) Å3. Its structure was refined from X‐ray powder diffraction data using the Rietveld method. The refinement of 25 instrumental and structural variables led to Rp = 10.2%, Rwp = 11.8%, Rexp = 7.7%, RB = 10.6%, S = 1.6 and χ2 = 2.6, for 5501 step intensities and 163 independent reflections. This compound is isostructural with Cu2GeSe3, and consists of a three‐dimensional arrangement of slightly distorted CuTe4 and SnTe4 tetrahedra connected by common corners. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

10.
    
The orthorhombic to tetragonal phase transition in (Ba0.92Ca0.08)(Zr0.05Ti0.95)O3 was investigated using high‐temperature X‐ray diffraction between 260 and 333 K. The results established the presence of tetragonal (P4mm) and orthorhombic (Amm2) phase co‐existence in the temperature range of 293 ≤T≤ 313 K. The tetragonal phase was found to increase from 27% at 293 K to 76% at 313 K. The structural refinement and line‐profile analysis ruled out the presence of an intermediate monoclinic structure during P4mm→Amm2 crossover. The analysis shows a pure orthorhombic (Amm2) structure for T < 293 K and tetragonal for T > 313 K.  相似文献   

11.
    
Single‐crystal of the CdGaCrSe(4‐X)S(X) system (x = 0; 1; 2; 3; 4) were grown by the chemical vapour‐phase transport technique. The crystals were obtaine by using CdCl2 as transporting agent for the composition with x = 1, and CrCl3 for those with x = 0; 2; 3 and 4. X‐ray powder diffraction analysis indicated that some of the samples crystallizes in the tetragonal system with space group I‐4 (CdGaCrSe3S , x = 1; CdGaCrSe2S2 , x = 2), or in a cubic system with space group Fd‐3m (CdGaCrSeS3, x = 3; CdGaCrS4, x = 4), however the sample of CdGaCrSe4 (x = 0) crystallizes in rhombohedral system. Magnetic measurements show significant changes in the magnetic interactions behaviour probably due to the anionic substitutions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

12.
    
Modern advanced diffraction experiments such as in situ diffraction, position‐resolved diffraction or diffraction tomography generate extremely large data sets with hundreds to many thousands of diffractograms. Analyzing such data sets by Rietveld refinement is hampered by the logistics of running the Rietveld refinement program, extracting and analyzing the results, and possibly re‐refining the data set based on an analysis of the preceding cycle of refinements. The complexity of the analysis may prevent some researchers either from performing the experiments or from conducting an exhaustive analysis of collected data. To this end, a MATLAB framework, MultiRef, which facilitates automated refinements, data extraction and intelligent choice of refinement model based on user choices, has been developed The use of MultiRef is illustrated on data sets from diffraction tomography, position‐resolved diffraction and in situ powder diffraction investigations of crystallization.  相似文献   

13.
    
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14.
    
This article describes a single‐shot methodology to derive an average coating thickness in multi‐particle core–shell systems exhibiting high X‐ray absorption. Powder composed of U–Mo alloy particles surrounded by a micrometre‐thick UO2 protective layer has been used as a test sample. Combining high‐energy X‐ray diffraction and laser granulometry, the average shell thickness could be accurately characterized. These results have been validated by additional measurements on single particles by two techniques: X‐ray nanotomography and high‐energy X‐ray diffraction. The presented single‐shot approach gives rise to many potential applications on core–shell systems and in particular on as‐fabricated heterogeneous nuclear fuels.  相似文献   

15.
    
A model sample consisting of two different hydroxyapatite (hAp) powders was used as a bone phantom to investigate the extent to which X‐ray diffraction tomography could map differences in hAp lattice constants and crystallite size. The diffraction data were collected at beamline 1‐ID, the Advanced Photon Source, using monochromatic 65 keV X‐radiation, a 25 × 25 µm pinhole beam and translation/rotation data collection. The diffraction pattern was reconstructed for each volume element (voxel) in the sample, and Rietveld refinement was used to determine the hAp lattice constants. The crystallite size for each voxel was also determined from the 00.2 hAp diffraction peak width. The results clearly show that differences between hAp powders could be measured with diffraction tomography.  相似文献   

16.
    
In situ powder X‐ray diffraction (PXRD) is a powerful characterization tool owing to its ability to provide time‐resolved information about phase composition, crystal structure and microstructure. The application of high‐flux synchrotron X‐ray beams and the development of custom‐built reactors have facilitated second‐scale time‐resolved studies of nanocrystallite formation and growth during solvothermal synthesis. The short exposure times required for good time resolution limit the data quality, while the employed high‐temperature–high‐pressure reactors further complicate data acquisition and treatment. Based on experience gathered during ten years of conducting in situ studies of solvothermal reactions at a number of different synchrotrons, a compilation of useful advice for conducting in situ PXRD experiments and data treatment is presented here. In addition, the reproducibility of the employed portable in situ PXRD setup, experimental procedure and data analysis is evaluated. This evaluation is based on repeated measurements of an LaB6 line‐profile standard throughout 5 d of beamtime and on the repetition of ten identical in situ synchrotron PXRD experiments on the hydrothermal formation of γ‐Fe2O3 nanocrystallites. The study reveals inconsistencies in the absolute structural and microstructural values extracted by Rietveld refinement and whole powder pattern modelling of the in situ PXRD data, but also illustrates the robustness of trends and relative changes in the extracted parameters. From the data, estimates of the effective errors and reproducibility of in situ PXRD studies of solvothermal nanocrystallite formation are provided.  相似文献   

17.
    
A single‐phase solid solution of Na0.5Bi0.5TiO3 (NBT) and BaZrO3 (BZ), i.e. (NBT)(1−x)(BaZrO3)x (x = 0.00, 0.01, 0.03, 0.05 and 0.07), was synthesized using the solid‐state reaction method. It is found that the temperature for single‐phase formation increases with increasing BZ content. A detailed structural investigation was carried out as a function of composition using Rietveld analysis of powder X‐ray diffraction data. The structural refinement reveals a crossover from monoclinic (Cc) to tetragonal (P4mm) symmetry in the composition range 0.03 < x < 0.05. The intensity of superlattice reflection due to a−a−c− tilting of oxygen octahedra in the Cc phase was found to decrease with increasing BZ content. The unit‐cell volume was also found to increase with BZ content, which was attributed to the higher ionic radii of Ba2+ and Zr4+ in comparison to Bi3+ (Na+) and Ti4+. The structural phase boundary observed in (NBT)(1−x)(BaZrO3)x is concurrent with the observation of morphotropic phase boundary like behaviour.  相似文献   

18.
    
A surface structure refinement procedure is introduced, which uses both anomalous and non‐anomalous crystal truncation rod data simultaneously. It is shown how a single structural model can be refined against data sets measured at different wavelengths and how this can greatly reduce correlations between fit parameters. The structure factors are computed taking into account the anomalous dispersion corrections and are scaled to the data, whereby each data set is assigned its own scale factor. The procedure is implemented in the widely used surface diffraction program ROD. The structure of a one unit cell thin LaAlO3 film on an SrTiO3(001) substrate is refined by making use of a non‐anomalous data set and one taken at the La L1‐edge.  相似文献   

19.
    
The structure determination of diclofenac embedded in a diclofenac‐containing chitosan matrix using conventional X‐ray powder diffraction data is demonstrated. It reveals that sodium diclofenac, the starting material in the preparation of a controlled‐release diclofenac‐containing chitosan matrix, changes to diclofenac acid in space group C2/c in the matrix. Simple methods were employed for handling the sample to obtain X‐ray powder diffraction data of sufficiently high quality for the determination of the crystal structure of diclofenac embedded in chitosan. These involved grinding and sieving several times through a micro‐mesh sieve to obtain a suitable particle size and a uniformly spherical particle shape. A traditional technique for structure solution from X‐ray powder diffraction data was applied. The X‐ray diffraction intensities were extracted using Le Bail's method. The structure was solved by direct methods from the extracted powder data and refined using the Rietveld method. For comparison, the single‐crystal structure of the same drug was also determined. The result shows that the crystal structure solved from conventional X‐ray powder diffraction data is in good agreement with that of the single crystal. The deviations of the differences in bond lengths and angles are of the order of 0.030 Å and 0.639°, respectively.  相似文献   

20.
    
The crystal structures of the 1,3,4 oxadiazole compounds N,N‐dimethyl‐N‐[4‐(1,3,4‐oxadiazol‐2‐yl)phenyl]amine ( 1 ) and 2‐methyl‐5‐phenyl‐1,3,4‐oxadiazole ( 2 ) have been determined. In case of 1 no adequate crystals were available; therefore the structure was solved at room temperature from X‐ray powder diffraction data using the method of simulated annealing. This solution is compared to a second one obtained by applying the molecular replacement method. Subsequent Rietveld refinements combined with the so called two stage method based on the data collected to 1.6 Å resolution yielded an Rwp value of 7.27% for 1 . Compound 1 crystallizes in the orthorhombic space group P212121 with lattice parameters of a = 7.599(4) Å, b = 6.004(2) Å, c = 21.736(3) Å. The crystal structure of 2 was solved by means of single crystal structure analysis (monoclinic space group P21/c, a = 8.010(3) Å, b = 10.783(4) Å, c = 19.234(7) Å, β = 90.794(9)°). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

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