Two compounds, [Co(NH3)5CO3]NO3·1/2H2O (labeled A) and [Co(NH3)4CO3]NO3·1/2H2O (labeled B), were obtained and characterized by X-ray powder diffraction. The samples were indexed using the programs TREOR90 and DICVOL91. In a monoclinic setting, the cell parameters are a=7.6661(3) Å, b=9.6212(3) Å, c=7.0725(4) Å, β=106.261(4)°, V=500.78 Å3, M20=36, F30=65 (0.0106, 44) for A and a=10.5623(5) Å, b=22.7304(18) Å, c=7.5174(5) Å, β=91.350(5)°, V=1804.31 Å3, M20=36, F30=82 (0.0071, 52) for B. The space group is probably P21/m(11) for A and P21/n(14) for B according to their reflection conditions.

Sm2Bi2Ti3O12 was synthesized by solid state reaction from Sm2O3, Bi2O3, and TiO2 in molar relation 1:1:3. Title compound is isostructural with Bi4Ti3O12. Products of the reaction were analyzed by X-ray diffraction methods. The crystal structure was refinement by the Rietveld Method. Cell parameters are: a=5.368(2), b=5.369(2), and c=32.71(2) Å, space group Fmmm. The final R value was 9.96% (Rw=13.43%).© 1998 International Center for Diffraction Data.

A nonlinear optical material, N-(p-methoxy benzoyl)-N′-(p-methyl phenyl) thiourea (C16H16N2O2S), has been characterized by X-ray powder diffraction. Experimental values of 2θ corrected for systematic errors, relative peak intensities, values of d, and the Miller indices of 94 observed reflections with 2θ up to 66° are reported. The powder diffraction data and the figure-of-merit are reported. The least-squares refined unit cell parameters are a=25.3291(3) Å, b=11.9478(1) Å, c=10.1407(4) Å, β=103.10(2)°, V=2988.97(6) Å3, Z=8, Dx=1.335(0) g/cm3, with space group P21(4).

The crystal structure of recently discovered chromium (III) dimagnesium trivanadate (V) Mg2CrV3O11 was refined using the Rietveld method. The crystal system of Mg2CrV3O11 is triclinic with space group P1− (Mg1.7Zn0.3GaV3O11 type) and lattice parameters a=6.4057(1) Å, b=6.8111(1) Å, c=10.0640(2) Å, α=97.523(1)°, β=103.351(1)°, γ=101.750(1)°, and Z=2. The characteristic feature of compounds in the A2BV3O11 (A=Mg, Zn and B=Ga, Fe, Cr) family is a strong tendency to share the octahedral M(1) and M(2) sites by both divalent A and trivalent B atoms, and the bipyramidal M(3) sites occupied by divalent A ions. In the present refinement, the only constraint assuming full occupancy of the M(1), M(2), and M(3) sites leads to the following Cr/(Cr+Mg) ratios: 0.70(2) at M(1), 0.24(2) at M(2), and 0.03(2) at M(3). These occupancies are discussed and compared to those of isotypic compounds. The values of interatomic distances are found to be comparable with those reported by R. D. Shannon in 1976. Electron paramagnetic resonance has been also analyzed. Two absorption lines with g≈2.0 (type I) and g≈1.98 (type II) have been recorded in the EPR spectra, and attributed to V4+ ions and Cr3+–Cr3+ ion pairs, respectively. The exchange constant J between Cr3+ ions has been calculated.

Synthesis and structure of two phosphates belonging to the ternary Sb2O5-Fe2O3-P2O5 system are reported. Structures of both SbV1.50FeIII0.50(PO4)3 and (SbV0.50FeIIIe0.50)P2O7 phases, obtained by solid state reaction in air atmosphere at 950 °C and 900 °C, respectively, were determined at room temperature from X-ray powder diffraction using the Rietveld method. Sb1.50Fe0.50(PO4)3 phosphate belongs to the Nasicon-type structure with R32 space group. Hexagonal cell parameters are ahex.=8.305(1) Å and chex.=22.035(2) Å. Rietveld refinement results show a 2-2 ordered distribution, along the c-axis, of X(1) and X(2) sites (crystallographic formula [Sb0.88Fe0.12]X(1)[Fe0.38Sb0.62]X(2)(PO4)3) in the Nasicon framework. (Sb0.50Fe0.50)P2O7 is isotypic with β-SbP2O7 pyrophosphate [Pna21 space group; a=7.865(1) Å, b=15.699(2) Å, c=7.847(1) Å]. Its crystal structure is built up from corner-shared SbO6 or FeO6 octahedra and P2O7 groups (two group types). Each P2O7 group shares its six vertices with three SbO6 and three FeO6 octahedra, and each octahedra is connected to six P2O7 groups. A quasi 1-1 ordered distribution, along the b-axis, of Sb5+ and Fe3+ ions in the pyrophosphate framework are observed.

Mixed solvent of ethanol and water using FeSO4⋅7H2O and (NH2)2CS as precursors with polyvinylpyrrolidone as surfactant was used to synthesize cubic FeS2 (pyrite) crystals. Crystalline phase and surface morphologies of the crystals were characterized by X-ray diffraction and scanning electron microscopy, respectively. Volume ratio of solvent, reaction temperature, reaction time, and sulfur source were found to be the key parameters for the formation of pure pyrite crystals. Optimal micron-size pyrite crystals were successfully grown from a mixed solvent of ethanol and water with a volume ratio of 3:2, heated to a reaction temperature of 180 °C, and maintained for 36 h with thiourea as the sulfur source.

Improved X-ray powder diffraction data for synthetic PdSn are reported. Powder diffraction data were collected with a laboratory X-ray source (CuKα) for Rietveld refinement. Refined crystallographic data for PdSn (orthorhombic, Pnma) are a=6.1388(4), b=3.89226(3), c=6.3377(4) Å, V=151.43(2) Å3, Z=4, and Dx=9.87 g∕cm3.

High resolution X-ray powder diffraction data have been collected with Bragg-Brentano geometry on samples of MgO using Ni-filtered and graphite-monochromated CuKαradiation. Selection of the characteristic radiation by Ni-filtering produces severe peak asymmetry, truncates the low-angle foot of the peak, lowers the general level of background on the low angle side, and leaves a remnant Kβpeak for all foils of reasonable thickness. When step-scan data produced by this method are used for Rietveld analysis, all of these features cause difficulties in fitting a smooth function to the background and in successfully modelling the detailed profiles of the peaks. On the other hand, Kαradiation from a diffracted-beam monochromator provides inherently more symmetric peaks and a smoothly varying background on both sides of the peak centre, both of which effects can be adequately modelled during Rietveld analysis. The primary disadvantage with monochromation is that, even with very careful setting of the pulse height discrimination, the monochromator may pass a small proportion of the λ/2 component of the incident radiation. In samples containing small quantities (i.e., 2 wt%, or less) of impurity phases, the undesirable features of the diffractometer profile (i.e., asymmetric and truncated background, and Kβand λ/2 peaks) can be of similar intensity to the main peaks arising from the impurities (as well as substructure peaks from the primary phases), thereby leading to difficulties in their identification and quantification. Nevertheless, with due care and long data collection times, the abundances of minor phases can be measured with Rietveld analysis down to levels of the order of 0.1 wt%.

Quantitative comparisons between patterns from PDF-4 and experimental data using the Integral Index method are presented. The software integrated into the PDF-4 (DDView+) provides the ability to calculate fully digitized diffraction patterns for all 272,232 entries (PDF-4+ 2007). To provide a means of quantitative comparison between entries in the Power Diffraction File (PDF) and experimental data obtained in the laboratory, data filtering using Boolean logic has been used to reduce the size of the comparison set. Within this comparison set, we have used the Integral Index method to provide quantitative comparisons between digitized patterns obtained from the PDF-4 and experimental data. The quantitative aspects facilitate total pattern matching, that is, selecting the pattern in the PDF-4 that most closely matches input experimental data. Several examples will be used to illustrate the pattern matching process and the utility of this approach will be examined.

Structural characterization and X-ray reference powder pattern determination have been conducted for the Co- and Zn-containing tridymite derivatives Ba(Co1−xZnx)SiO4 (x = 0.2, 0.4, 0.6, 0.8). The bright blue series of Ba(Co1−xZnx)SiO4 crystallized in the hexagonal P63 space group (No. 173), with Z = 6. While the lattice parameter “a” decreases from 9.126 (2) Å to 9.10374(6) Å from x = 0.2 to 0.8, the lattice parameter “c” increases from 8.69477(12) Å to 8.72200(10) Å, respectively. Apparently, despite the similarity of ionic sizes of Zn2+ and Co2+, these opposing trends are due to the framework tetrahedral tilting of (ZnCo)O4. The lattice volume, V, remains comparable between 626.27 Å3 and 626.017 (7) Å3 from x = 0 to x = 0.8. UV-visible absorption spectrum measurements indicate the band gap of these two materials to be ≈3.3 and ≈3.5 eV, respectively, therefore potential UV photocatalytic materials. Reference powder X-ray diffraction patterns of these compounds have been submitted to be included in the Powder Diffraction File (PDF).

Knowledge of the errors in a diffraction measurement of residual strains and stresses is useful information, not only in its own right, but also because it permits automation of a measurement to an operator-specified precision. There are three sources of these errors.

A brief description of the theoretical approach of this new method is given. The main purpose of the method is to correlate in a more logical order not only the data yielding the two laws relating mass-absorption coefficient to wavelength and to atomic number, respectively, but also to delineate, within two discontinuities, the relationship existing between each value and the other ones taken as a whole. The empirical equation relating μ to λ is μ = Cλn. A table of complete values for the constant C and die power n to be assigned in the equation is given for finding the values of mass-absorption coefficients above unity for all elements (except hydrogen) and for all wavelengths between 0.17837 and 10 A. It is believed that until a complete set of experimental data obtained with modern equipment is available, this proposed method fills the enormous gaps between actual compiled values.

Two metal foils, one pure plutonium and the other being a solid solution of 6.5 a/o gallium In plutonium, were examined, in-situ, by X-ray diffraction techniques while under pressure. The purpose was to determine the compression and compressibility of these materials as a function of pressure and to identify the products of any transformation that may occur due to the action of applied pressures.

As is well known, the fluorescent yield decreases very rapidly with the atomic number with the result, for example, that sensitive sodium and magnesium analysis is extremely difficult if not impossible with conventional X-ray spectrographs. It is demonstrated, however, that analysis for sodium and magnesium can be accomplished with sensitivity comparable to that conventionally obtained for elements such as aluminum, silicon, and phosphorous, providing that the conditions for excitation and measurement of the associated soft X-radiations are optimized, A high-intensity demountable tube using an aluminum anode has been developed which can be used interchangeably with the conventional spectrographic X-ray source. This provides a large amount of incident radiation, aluminum foil filtered, optimally close in wavelength to that of the line radiation being excited. A gypsum analyzing crystal is used along with greatly reduced beam collimation. The standard flow proportional counter and pulse height discrimination is employed. An appropriate filter, such as aluminum foil, is used as a window for the counter1 to provide further discrimination and enhanced signal-to-background ratio.

Some kinds of plastic deformation leave a residual pseudo-macrostress in the material. The existence of this stress in certain specimens introduces errors into the standard x-ray measurement of residual macrostress, namely, in specimens that have been stretched, compressed, bent, rolled, or drawn.

No error is involved in x-ray measurements on peened, ground, or machined surfaces, or in specimens where the source of the stress is remote from the surface examined.

The x-ray and magnetic evidence for pseudo-macrostress is reviewed.

The use of quantitative x-ray diffraction (XRD) as an analytical technique has recently become increasingly popular. There ate primarily two reasons for this increasing interest in a relatively old discipline. The first is simply the need for quantitative phase analysis. This need arises from several sources such as government regulations on respiratory quartz, industrial quality control, and material research. X-ray diffraction provides a readily available technique for bulk phase analysis on chemically similiar phases. For phases which are elementally distinct, our sister science, x-ray fluorescence, can more easily provide the quantitation needed. The second reason for the increasing interest in quantitative XRD is the ready availability of automated powder diffractometers. These instruments remove much of the tedium involved in the collection and reduction of the data.

While the theoretical basis for the correction of non-linearity of detector systems is well known, methods for the determination of dead-time effects must be adapted to electron probe microanalyzer systems. Two such methods, one employing both X-ray and current measurements and the other employing simultaneous X-ray measurements on two spectrometers, are described. The effect of pulse-height shrinkage at high counting rates on the linearity of the detector system is discussed. When the proposed corrections for the dead-time of X-ray detector systems employing proportional counters are applied to the X-ray intensity measurements obtained with the electron probe microanalyzer, count rates as high as 50,000 counts/sec can be used.

Systematic procedures are used for generating the geometrically possible close-packed ordered layers for any desired binary “ideal composition” and the various geometrically possible stacking sequences with a given number of layers of known structure. The known ordered close-packed cyrstal structure types in AB3 and AB4 alloys are characterized by the structure of the layer and by the stacking sequence. Their occurrence is reviewed in relation to pertinent variables, such as electron concentration and atomic size.

A comprehensive Fortran IV program designed to perform the matrix correction in x-ray fluorescence analysis is described. Specimens and standards can be in bulk or film form. All necessary fundamental parameters are provided by internal routines thereby requiring a minimum of input data.