Powder Diffraction Lines Research Articles

Changchengite—A New Iridium Bismuthide–Sulphide from the Yanshan Mountains

AbstractChangchengite occurs in chromite orebodies in dunite and in platinum placer deposits in chromite orebodies nearby. The mineral occurs as massive aggregates or veinlets on margins of iridisite (IrS2) and replaces it. Opaque. Lustre metallic. Colour steel–black. Streak black. Hm = 3.7. VHN20= 165 kg/mm2. Isotropic. Cleavage none. Density 11.96 g/cm3. Seven electron microprobe analyses give the following mean chemical results (wt. %): S 7.2, Cu 0.3, Te 0.4, Ir 41.2, Pt 2.8 and Bi 47.3 with total 99.1. The simplified formula is IrBiS. The strongest X–ray powder diffraction lines (hkl, d, f) are 210, 2.75 (70); 211, 2.51 (60); 311, 1.860 (100); 440, 1.090 (50) and 600, 1.027 (50). The X–ray powder diffraction pattern is similar to that of mayingite. After the diffraction data are indexed the mineral is determined to be cubic. The space group is P 213 with a = 0.6164(4) nm, V = 0.2342 nm3 and Z = 4.

Lukechangite-(Ce), a new rare-earth-fluorocarbonate mineral from Mont Saint-Hilaire, Quebec

Other| December 01, 1997 Lukechangite-(Ce), a new rare-earth-fluorocarbonate mineral from Mont Saint-Hilaire, Quebec Joel D. Grice; Joel D. Grice Canadian Museum of Nature, Research Division, Ottawa, ON, Canada Search for other works by this author on: GSW Google Scholar George Y. Chao George Y. Chao Carleton University, Canada Search for other works by this author on: GSW Google Scholar American Mineralogist (1997) 82 (11-12): 1255–1260. https://doi.org/10.2138/am-1997-11-1220 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Joel D. Grice, George Y. Chao; Lukechangite-(Ce), a new rare-earth-fluorocarbonate mineral from Mont Saint-Hilaire, Quebec. American Mineralogist 1997;; 82 (11-12): 1255–1260. doi: https://doi.org/10.2138/am-1997-11-1220 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Lukechangite-(Ce), ideally Na3Ce2(CO3)4F, is a new mineral from Mont Saint-Hilaire, Quebec. It occurs as tabular, short prismatic, and barrel-shaped crystals up to 1 mm. It is colorless to pale beige with a white streak and a vitreous, or somewhat pearly on {0001}, luster. Associated minerals include microcline, analcime, sodalite, aegirine, serandite, eudialyte, catapleiite, fluorite, petersenite-(Ce), siderite, astrophyllite, and albite. Lukechangite-(Ce) is soft, Mohs hardness ≈ 4½, brittle, with an uneven to conchoidal fracture, and with perfect {0001} cleavage. Lukechangite-(Ce) is uniaxial negative, ω = 1.728(3) and ϵ = 1.542(1). It is hexagonal, space group P63/mmc, a = 5.068(1), c = 22.87(5) Å, V = 509(1) Å3, and Z = 2. The strongest X-ray powder diffraction lines [d (Å), I, hkl] are: 5.71(50)(004), 4.31(100)(101), 3.804(50)(006), 3.169(70)(105), 2.877(60)(106), 2.534(70)(110), 2.192(90B)(109,200,201), 1.978(70)(205), and 1.658(50)(209,210,211). An average of the electron-microprobe analyses gave Na2O 14.94, CaO 0.10, SrO 0.12, La2O3 16.36, Ce2O3 29.48, Pr2O3 1.95, Nd2O3 5.88, F 3.58, CO2 (28.40), and O ≡ F – 1.51, total 99.30 wt%. CO2 was calculated by stoichiometry from the results of the crystal-structure analysis. Dcalc is 4.02 g/cm3. The atomic arrangement of lukechangite-(Ce) has been refined to R = 3.4%. The structure is layered parallel to (001), with CO3 groups oriented parallel to the layering forming thick slabs incorporating either Ce or Na cations and a separate Na-F layer. The structure of lukechangite-(Ce) resembles that of huanghoite-(Ce) and baiyuneboite-(Ce) and is isostructural with synthetic Na3La2(CO3)4F. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.

Structural phase transitions in KMnF3 doped by Li+, Na+ and Rb+

Profile analysis of powder diffraction lines was used to determine the changes of the lattice parameters versus temperature in KMnF3 doped by Li+, Na+ and Rb+ cations. The temperatures of the structural phase transitions (SPT), the type of distortion and the phase diagram in the concentration rangex<0.15were determined from the splitting of some cubic lines as 211, 220 and 400. The discussion of the order of the SPT as a function of concentration is presented.

Broadening of x-ray powder diffraction lines under nonhydrostatic stress

Examining the effect of nonhydrostaticity on the shape of x-ray powder diffraction lines shows that a uniaxial stress field, as is generated in opposed-anvil type high-pressure apparatuses, can result in lines being split or having an asymmetric shape. The distribution of local stresses, generated by mismatches in shapes of neighboring grains within the specimen, results in orientation-dependent broadening: diffraction linewidths are generally proportional to 1/E(hkl), where E(hkl) is Young’s modulus for plane hkl. Since anomalous diffraction patterns can be misinterpreted as indicating a phase transformation, the occurrence of new phases under nonhydrostatic pressure should be carefully confirmed.

Optical and X-ray evidence of structural phase transitions in mixed (Rb1−xKx)CaF3crystals

Abstract Structural phase transitions have been found in the mixed fluoroperovskites crystals (Rb1−xKx)CaF3 (x=0.05, 0.2, 0.35, 0.5, 0.88, 1.0) by optical birefringence and X-ray diffraction. Profile analysis of powder diffraction lines was performed to determine the change of lattice parameters versus temperature in order to establish the crystal symmetry of each structural phase and to measure the temperatures of the transitions. From the splitting of the 400 cubic Bragg line and consideration of Glazer's classification of tilted octahedra in perovskites, the various types of distortions were found. Sequences of CaF6 tilting octahedra occurring during the phase transitions are suggested and discussed for each concentration.

Applicabilities of the Warren–Averbach analysis and an alternative analysis for separation of size and strain broadening

The validities of the Warren–Averbach analysis and of an alternative analysis for separation of size and strain contributions to diffraction line broadening are investigated. The analyses are applied to simulated and experimental line profiles. The Fourier coefficients of the simulated line profiles are derived from expressions for the distortion field around specific lattice defects: misfitting inclusions and small-angle grain boundaries. Applicability tests are also performed on experimental powder diffraction line profiles taken from plastically deformed specimens: thin aluminium layers and ball-milled molybdenum powders. It is concluded that for both methods finite but different classes of specimen exist for which they give meaningful results. In practice, each time an analysis is performed the results must be tested against common (physical) sense and all information available on the specimens.

An Analysis of the Effect of Different Instrumental Conditions on the Shapes of X-ray Powder Line Profiles

Abstract In this investigation we have examined how the full width at half maximum intensity (FWHM) and asymmetry of x-ray powder diffraction line profiles are influenced by the instrumental conditions adopted. Experimental x-ray data has been collected for a matrix of instrumental conditions by systematically varying the divergence slit angle (and the corresponding anti-scatter slit) over the range 0.25° to 1.25°, by using either a 0.05mm or 0.2mm receiving slit, or by removing the diffracted beam Soller slit. The line profile Standard Reference Material, SRM, 660 (LaB6) was used as the powder specimen in that it imparts minimal specimen induced broadening to the diffraction profiles. X-ray data were collected on a conventional, divergent beam, x-ray diffractometer using CuKα radiation. The FWHM of the CuKα1 component can be as low as 0.035°2θ for high resolution conditions, but is normally ∼0.1°2θ at 2θ ≈ 30° for the instrumental conditions adopted in routine diffractometry. Below 2θ = 50°, the divergence slit has a significant effect on the FWHM and is the major cause of the increase in FWHM with decreasing 2θ. Results are presented of the 2θ dependence of FWHM values for each of the instrumental conditions recorded. A general relationship for the 2θ dependence of the FWHM and the asymmetry has been investigated to supersede the inappropriate Cagliotti expression frequently used in x-ray Rietvcld refinement.

Ravatite, C14H10, a new organic mineral species from Ravat, Tadzhikistan

The new organic mineral ravatite (analyzed as C 14.1 H 9.9 , idealized formula C 14 H 10 ), identical with synthetic phenanthrene, is described as a sublimation product caused by the natural combustion of a brown coal seam near Ravat/Tadzhikistan (southwestern Tjan' Shan'). It forms thin, platelet-like individuals with diameters of mainly a few hundred micrometers which are usually aggregated to thin crusts on a bituminous, H 2 SO 4 -impregnated coaly-earthy material. Ravatite is colourless, or―dependent on the amount of coaly, gas and other inclusions―white to pale grey and transparent to translucent. It shows a vitreous to wax-like lustre. Ravatite has a monoclinic lattice (space group P2 1 ) with a o = 8.392(5)A; b o = 6.181(3)A; co = 9.558(5)A; β = 98.48(12)°; V = 490.4(4)A 3 ; Z = 2. The observed strongest five X-ray powder diffraction lines [d in A (I rel ) (hkl)] are: 9.434(100)(001); 4.028(13)(201); 4.941(11)(110); 4.724(11)(002); 3.371(10)(211). The Mohs hardness is about 1; the calculated and the measured densities are 1,207(1) and 1.11(2) g/cm 3 , respectively. Ravatite shows a whitish-yellow fluorescence under ultraviolet light. The initial temperature of melting is 94.3 °C. Infrared absorption and Raman data do not differ significantly from data of synthetic phenanthrene

X-Ray Diffraction Line Broadening: Modeling and Applications to High-Tc Superconductors.

A method to analyze powder-diffraction line broadening is proposed and applied to some novel high-Tc superconductors. Assuming that both size-broadened and strain-broadened profiles of the pure-specimen profile are described with a Voigt function, it is shown that the analysis of Fourier coefficients leads to the Warren-Averbach method of separation of size and strain contributions. The analysis of size coefficients shows that the “hook” effect occurs when the Cauchy content of the size-broadened profile is underestimated. The ratio of volume-weighted and surface-weighted domain sizes can change from ~1.31 for the minimum allowed Cauchy content to 2 when the size-broadened profile is given solely by a Cauchy function. If the distortion co-efficient is approximated by a harmonic term, mean-square strains decrease linearly with the increase of the averaging distance. The local strain is finite only in the case of pure-Gauss strain broadening because strains are then independent of averaging distance. Errors of root-mean-square strains as well as domain sizes were evaluated. The method was applied to two cubic structures with average volume-weighted domain sizes up to 3600 Å, as well as to tetragonal and orthorhombic (La-Sr)2CuO4, which exhibit weak line broadenings and highly overlapping reflections. Comparison with the integral-breadth methods is given. Reliability of the method is discussed in the case of a cluster of the overlapping peaks. The analysis of La2CuO4 and La1.85M0.15CuO4(M = Ca, Ba, Sr) high-Tc superconductors showed that microstrains and incoherently diffracting domain sizes are highly anisotropic. In the superconductors, stacking-fault probability increases with increasing Tc; microstrain decreases. In La2CuO4, different broadening of (h00) and (0k0) reflections is not caused by stacking faults; it might arise from lower crystallographic symmetiy. The analysis of Bi-Cu-O superconductors showed much higher strains in the [001] direction than in the basal a-b plane. This may be caused by stacking disorder along the c-axis, because of the two-dimensional weakly bonded BiO double layers. Results for the specimen containing two related high-Tc phases indicate a possible mechanism for the phase transformation by the growth of faulted regions of the major phase.

Structural phase transitions in (K1-xNax)MnF3 and (K1-xLix)MnF3 mixed perovskite crystals

Profile analysis of powder diffraction lines was used to determine the variations in lattice parameters as a function of temperature. Using this procedure, phase diagrams of (K1-xNax)MnF3 and (K1-xLix)MnF3 were obtained in the concentration range x<or=0.02. From the splitting of cubic (220) and (400) Bragg's lines the temperatures of the structural phase transitions and the types of distortion were determined. The following sequence of distortions was observed: cubic to tetragonal to orthorhombic to monoclinic.

Synthesis, structural investigation, and physical characterization of chromium fluoride/graphite intercalation compounds

Intercalation into graphite of CrF 4 containing some amounts of CrF 5 has been investigated using anhydrous HF solutions. Stage-2 GICs are generally obtained with repeat distance I c =11.45 Å, whatever the pristine graphite material. The I c value corresponds to CrF 6 octahedra with two faces lying parallel to the graphene layers. The fitting of the intensities of the (00 l ) powder diffraction lines and the relationships between the unit cells of the graphite and of the intercalate sublattices leads to a theoretical C 18 CrF 4.5 formulation which is in good agreement with the observed composition, i.e., C x CrF 4.5 with 17≤ x ≤21. XANES. ESR, and magnetic measurements have confirmed the (+IV) oxidation state of the intercalated chromium and have corroborated the charge transfer evaluation from reflectivity data.

X-ray powder diffraction line profiles by Fourier synthesis

This work presents a new method of synthesizing the reflection profile, based on the calculation of Fourier coefficients of instrumental functions. The classification and construction of Fourier coefficients are effected, in a general way, from the analysis of the possible paths of beams in the diffractometer. Relationships were obtained which made it possible to synthesize the line profiles in different experimental conditions. The possibility of calculating the reflection profiles of a standard (annealed BaF2) without introducing varying profile parameters is shown. Better results in describing the reflection profiles have been obtained than by applying the Pearson VII function with varying profile parameters.

Electron and X-ray diffraction from antiphase domains in the barium magnesium hollandite Ba1.33Mg1.33Ti6.67O16

The barium hollandite Ba1.33Mg1.33Ti6.67O16 undergoes an order–disorder transition at 1100 (10) K. Below this temperature the Ba and vacant sites in the tunnels of the hollandite structure are ordered with the sequence Ba–Ba–vacancy and b = 3bhollandite. At the same time, antiphase domains form which produce broadened X-ray diffraction lines and electron diffraction peaks shifted off their commensurate superstructure positions. This shift in the diffraction peaks is explained by the formation of a boundary layer with a spacing of 2.5bhollandite between adjacent domains. Equations are developed relating the peak shift to the domain size which are consistent with observed electron diffraction patterns. The theory is extended to interpret the broadening of X-ray powder diffraction lines. During the early stages of domain growth boundaries form on (101), (10\overline 1) and (010) planes. Domain growth occurs mainly in the [101] and [10\overline 1] directions and after extended annealing only (010) boundaries remain.

Synchrotron and Laboratory Studies Utilizing a New Powder Diffraction Technique

AbstractWe have developed a new type of powder diffractometer. The diffractometer has the potential of both high count rates and very high resolution when used at a synchrotron source. The laboratory based instrument can achieve an order of magnitude improvement in count rate over existing methods with proper optics. The method uses a focusing diffracted beam monochromator in combination with a multichannel detector. The incident x-rays fall on a flat plate or capillary sample and are intercepted by a bent focusing monochromator which has the focus of the bend at the sample surface. The powder diffraction lines emerging from the bent crystal monochromator are detected by a linear or 2-dimensional detector. This allows us to eliminate the background from fluorescence or other scattering and to take data over a range of 3° to 4° instead of one angle at a time thereby providing a large improvement over conventional diffractometers.

Determination of the direction of the propagation vector for incommensurate structures from neutron powder diffraction patterns

A method is presented for indexing the powder diffraction lines from incommensurate structures by a systematic search of reciprocal space, choosing a propagation vector length derived from a satellite reflection in the powder diagram. An interactive computer program gives a graphical display of the direction of the propagation vector which gives the best fit to the pattern.

Redetermination of the Crystal Structure of Vesignieite

Abstract Vesignieite, Cu3Ba(VO4)2(OH)2, crystallizes in space group C2/ m with a ° = 1.0270(2), b ° =0.5911(1), c° = 0.7711(2)nm and β =116.42(3)°. The intensity data were collected with the RIGAKU RASA‐IIS single‐crystal four‐circle diffractometer. The structure was determined by Patterson and Fourier methods and refined by the least‐square technique to a final R index of 0.051 for 614 independent diffraction points with |F| &gt; 3σ| F|.The crystal structure analysis shows that vesignieite has a layer structure parallel to (001).The powder diffraction lines were reindexed.

A Correction for Truncation of Powder Diffraction Line Profiles

A Correction for Truncation of Powder Diffraction Line Profiles

Toyohaite, Ag&lt;SUB&gt;2&lt;/SUB&gt;FeSn&lt;SUB&gt;3&lt;/SUB&gt;S&lt;SUB&gt;8&lt;/SUB&gt;, a new mineral

Toyohaite, Ag2FeSn3S8, tetragonal, I41⁄a, a=7.464, c=10.80A, Z=2, is a new mineral corresponding to the Ag analogue of rhodostannite. Microprobe analyses demonstrate partial substitutions of Cu for Ag and Zn for Fe. The most Ag-rich and poor analyses are: Ag 24.39, 16.31; Cu: 0.14, 5.15; Fe 6.28, 6.18; Zn 0.37, 1.29; Cd 0.22, 0.14; Sn 41.24, 42.01; In 0.05, 0.17; totals 100.86%, 99.65%. They correspond respectively to: (Ag1.95Cu0.02)Σ1.97(Fe0.97Zn0.05Cd0.02)Σ1.04Sn2.99S7.57, and (Ag1.26Cu0.68) Σ1.94(Fe0.92Zn0.16Cd0.01) Σ1.09(Sn2.95In0.01) Σ2.96S7.39 (basis: total metal=6). Calculated density is 4.94 g/cm3. Toyohaite has a rhodostannite-like brown reflection color with very weak dichroism and distinct to strong anisotropism. Reflectances are: 23.5–24.3% (480nm); 24.1–26.1% (546nm) 24.7–26.4% (589nm); 26.5–28.3% (650nm). X-ray powder diffraction lines and their relative intensities: 3.72(35), 3.21(100), 2.03(35) and 1.882(35). It occurs as irregular-shaped poly crystalline aggregates up to 200 μm across in a massive pyrite-sphalerite ore from the Sorachi vein of the Toyoha mine, Sapporo, Hokkaido, Japan. The intimate associates include rhodostannite, hocartite, teallite, herzenbergite, and berndtite.

Desummation of Mixed Powder Diffraction Lines

Desummation of Mixed Powder Diffraction Lines

Effect of heavy atom disorder on the intensities of powder XRD lines of YBa2Cu3O7-y

Abstract It is shown that heavy atom disorder resulting from Y ↔ Ba, Ba ↔ Cu and Y ↔ Cu interchanges due to local stoichiometric constraints can cause significant changes in the intensities of X-ray powder diffraction lines of YBa2Cu3O7-y . A comparison of the theoretically predicted intensities with published patterns for specimens prepared by the conventional dry route reveals that Ba ↔ Cu interchanges involving copper atoms in the CuO2 planes can occur quite frequently and may be mistaken for (00l) texture.