Academic literature on the topic 'X-Ray powder Diffraction (XRD)'

Abstract A prototype instrument, which provides x-ray powder diffraction and x-ray fluorescence analysis in a compact unit, has been developed to support the needs of NASA for planetary exploration. The instrument uses a 9-watt Fe-anodc x-ray tube and CCD in a fixed geometry for recording powder patterns with a 2θ range of 35°. The fluorescence spectrum for elements below Fe is collected simultaneously with the diffraction data. A shuttered Cd-109 isotopic source with emissions at 22 and 80 keV is used to excite higher energy fluorescence. The low-energy limit for discriminating single photon events was found to be ∼1.5 keV. Al-K could be distinguished from a pure sample, but the spectrum below 6 keV was degraded by the read noise of the CCD, which introduced spectral artifacts. Diffraction peaks from halite had a FWHM of ∼1°(2θ), with major contributions to the width from the use of slit collimation on the source and the low tilt angle of the sample.

X-ray powder diffraction data for In3.85Zr2.80Sn0.35O12 are reported. The powders were prepared using a wet-chemical precipitation method. The XRD data could be fitted with a rhombohedral unit cell in space group R3 (No. 148). The Rietveld refined unit cell parameters are a=0.951 49(2) nm and c=0.889 51(2)nm in a hexagonal setting with Z=3 and Dx=6.69(1)g/cm3.

The structure of La2LiTaO6 has been derived from the powder X-ray powder diffraction (XRD) data. La2LiTaO6 is monoclinic with unit-cell parameters a = 5.621(1) Å, b = 5.776(1) Å, c = 7.954(2) Å, β = 90.34(2)°, space group P21/n (14), and Z = 2. The structure of La2LiTaO6 is an ordered perovskite with alternating Li and Ta octahedra. A new set of powder XRD data (d-spacing and intensity listing) has been generated to replace entry 00-039-0897 within the Powder Diffraction File. The newly elucidated structural data for La2LiTaO6 shall facilitate quantitative analysis of this impurity phase which is often observed during synthesis of the fast-ion conductor phase Li5La3Ta2O12.

Bismuth sulfide preparation and its x-ray diffraction studies are reported in this paper. The author have synthesized Bi2Sx (x = 3.15, 3.45) compound material with different sulfur content by conventional high temperature solid state solvothermal reaction of bismuth and sulfur which conforms that the (121) preferred orientation with crystallite size ~30 nm and splitting of peaks due to orthorhombic structure matches well with the standard data and demonstrate good crystalline quality and structural homogeneity of synthesized powder.This paper also describes the synthesis and x-ray diffraction studies of bismuth sulfide powder via versatile precipitation technique . Bismuth sulfide powder was synthesized using thiourea and sodium dodecyl sulfate or in absence of any surfactant maintained at 800C for 12 h keeping pH of solution constant at 1.4. Synthesized powder was characterized by x-ray diffraction technique which indicates that surfactants play major role in synthesis of bismuth sulfide that conforms the crystallite size ~35 nm. The employed solid state solvothermal technique played an important role to progress the homogeneous reaction and preparation of pure and fine bismuth sulfide powder. The possible application of this material in photovoltaic devices is suggested.

X-ray powder diffraction data for Mo2.85Al1.91Si4.81 are reported. The new Mo2.85Al1.91Si4.81 compound was successfully prepared using the self-propagating high-temperature synthesis (SHS) technique. The starting atomic mixture of reactant powders was Mo+2(1−x)Si+2xAl with x=0.3. The final powder compound obtained by the SHS technique was determined to be Mo2.85Al1.91Si4.81 by ICP-AES. X-ray powder diffraction pattern of Mo2.85Al1.91Si4.81 was recorded using an X-ray powder diffractometer, Cu Kα radiation, and analyzed by automatic indexing programs. Mo2.85Al1.91Si4.81 was found to be hexagonal with a=4.6929(2) Å and c=6.5515(4) Å. The XRD results are in good agreement with those of Mo2.85Ga2Si4.15.

The CeCo3Ni2 compound was synthesized by arc melting under argon atmosphere. High-quality powder X-ray diffraction (XRD) data of CeCo3Ni2 have been collected using a Rigaku SmartLab X-ray powder diffractometer. The refinement of the XRD pattern for the CeCo3Ni2 compound shows that the CeCo3Ni2 is a hexagonal structure, space group P6/mmm (No.191) with a = b = 4.9081(2) Å, c = 4.0034(2) Å, V = 83.52 Å3, Z = 1, and ρx = 8.6347 g cm−3. The Smith–Snyder FOM F30 = 112.7(0.0089, 30) and the intensity ratio RIR = 0.48.

A parallel-beam X-ray diffraction geometry using X-ray guide tubes is proposed to eliminate preferred-orientation effects in powder X-ray diffraction (XRD) patterns and for new applications of XRD. A bundle of X-ray guide tubes (polycapillaries) is used to provide an intense quasi-parallel (approximately 0.2° divergence) and large-diameter (approximately 20 mm) beam of X-rays needed for parallel-beam diffractometry. Mica and silicon particles were agitated inside a cylindrical chamber by a steady flow of N2gas so that they were randomly oriented. The quasi-parallel incident X-ray beam passed through the cloud of floating particles. The diffracted X-rays were detected using a standard 2θ diffractometer. The integrated intensities observed agree well with those calculated from the known model of the crystal structure. This result demonstrates that this type of diffractometry is capable of avoiding preferred-orientation effects and of collecting XRD data for moving powder samples.

X-ray powder diffraction data for three new bismuth yttrium ytterbium oxide compounds synthesized by solid-state reaction method are reported. The unit-cell dimensions were determined from X-ray diffraction method using Cu Kα radiation and evaluated by indexing programs. The cubic δ-Bi2O3 phase was identified to be the sole crystalline phase in Bi0.82Y0.09Yb0.09O1.5, Bi0.82Y0.12Yb0.06O1.5, and Bi0.82Y0.06Yb0.12O1.5 with lattice constants of a=5.5110(3), 5.5154(2), and 5.5113(2) Å, respectively.

The diffracted x-rays from a polycrystalline (powder) sample form a series diffraction cones in space since large numbers of crystals oriented randomly in the space are covered by the incident x-ray beam. Each diffraction cone corresponds to the diffraction from the same family of crystalline planes in all the participating grains. When a two-dimensional (2D) detector is used for x-ray powder diffraction, the diffraction cones are intercepted by the 2D detector and the x-ray intensity distribution on the sensing area is converted to an image-like diffraction pattern. The 2D pattern contains the scattering intensity distribution as a function of two orthogonal angles. One is the Bragg angle 2θ and the other is the azimuthal angle about the incident x-ray beam, denoted by γ. A 2D diffraction pattern can be analyzed directly or by data reduction to the intensity distribution along γ or 2θ. The γ-integration can reduce the 2D pattern into a diffraction profile analogs to the conventional diffraction pattern which is the diffraction intensity distribution as a function of 2θ angles. This kind of diffraction pattern can be evaluated by most exiting software and algorithms for conventional applications, such as, phase identification, structure refinement and 2θ-profile analysis. However, the materials structure information associated to the intensity distribution along γ direction is lost through γ-integration. The intensity distribution and 2θ variations along γ contain more information, such as the orientation distribution, strain states, crystallite size and shape distribution. In order to understand and analyze 2D diffraction data, new approaches and algorithms are necessary. The diffraction vector approach has been approved to be the genuine theory in 2D data analysis. The unit diffraction vector used for 2D analysis is a function of both 2θ and γ. The unit diffraction vector for all the pixels in the 2D pattern measured in the laboratory coordinates can be transformed to the sample coordinates. The vector components can then be used to derive fundamental equations for many applications, including stress, texture, crystal orientation and crystal size evaluation by γ-profile analysis. The unit diffraction vector is also used in polarization and absorption correction.

The CheMin instrument on the Curiosity rover measures XRD and XRF data using Co radiation in transmission geometry. It has analyzed <150 μm portions of eolian soil (Rocknest) and two drill-hole powders (John Klein and Cumberland) from a mudstone [1, 2, Figure 1]. XRD data for Rocknest soil revealed plagioclase, forsteritic olivine, augite, and pigeonite. John Klein and Cumberland are similar, with much less Fe-forsterite and more magnetite than Rocknest. Data were analyzed via Rietveld methods (Topas), and profiles were modeled using beryl-quartz data measured on Mars. CheMin's broad profiles limited analysis of minor phases (<3 wt. %), although the presence of minor phases was evaluated individually for every sample by including each in the Rietveld model and evaluating their effect on the fit. We found no evidence for any perchlorate, carbonate, or sulfate mineral (apart from anhydrite, and bassanite in the mudstones). No phyllosilicate was detected in the soil, but mudstone samples contained two different phyllosilicates, likely trioctahedral smectites. The John Klein XRD pattern had a broad ~10Å peak, whereas Cumberland showed broad peaks at ~13.2Å and ~10Å. The background in all XRD patterns suggested the presence of amorphous/poorly ordered components, which were analyzed using FULLPAT, giving ~27% amorphous content in Rocknest and ~20% in the mudstones. This mineralogy is very similar to that found in soils on the flanks of Mauna Kea volcano, Hawaii. Mineralogy differences between the Rocknest material and the mudstones may be explained by alteration of Fe-forsterite to smectite + magnetite. Combining these results with compositional estimates from unit-cell parameters and bulk chemistry will allow determinations of individual phase compositions, including that of the amorphous component(s). The exact nature of the amorphous component is unclear, but other data show that it is hydrous.