X-ray powder diffraction data and refined unit cell parameters for SrTi3Nb4O17, SrTi5Nb4O21, SrTi7Nb4O25, SrTi9Nb4O29, SrTi11Nb4O33, SrTi13Nb4O37, and SrTi15Nb4O41 are reported here. The powder patterns for these oxides suggest that they form a homologous series SrM2n+1O4n+5 (M=Ti, Nb; n=3→9), which is isostructural with the orthorhombic “chemically twinned rutile” series found previously in the K2O-TiO2-Ta2O5 and BaO-TiO2-Nb2O5 systems. The structures are built of corner-sharing slabs of the rutile structure; successive members are generated by adding 2TiO2 to the slab thickness of the previous member. The series crystallizes in space group Cmcm (No. 63), with members exhibiting similar a-, b-dimensions (∼6.6, ∼8.9 Å; respectively), and c-dimensions that linearly increase (by ∼4.4 Å per member) from 20.8 Å for n=3 to 47.1 Å for n=9.

A nonlinear optical material, o–chlorobenzol–benzoyl thiourea (C14H11ClN2OS), 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 78 observed reflection with 2θ up to 72° are reported. The powder diffraction data have been evaluated, and the figures-of-merit are reported. The unit cell parameters least-squares refined from 28 nonoverlapping peaks of the monoclinic compound with a P2 space group are a=13.2797(4) Å, b=12.4058(8) Å, c=8.1561(2) Å, β=95.398(1)°, V=1337.7(4) Å3, Z=4, Dx=1.444 g/cm3. © 1997 International Centre for Diffraction Data.

The Metals and Alloys Indexes, published by the International Centre for Diffraction Data, contain four indexes. These are: (a) the alphabetical formula index (AFI); (b) the Pearson symbol code index; (c) the common name index; and (d) the Strukturbericht symbol index. These indexes (which contain metals, alloys, and related phases in the Powder Diffraction File) have been designed to be used independently or in conjunction with the Powder Diffraction File to facilitate the characterization of materials. All data in these indexes have been critically reviewed. The organization, selection of materials, and use of alphabetical formulas are similar to those of standard metallurgical references such as Pearson or Villars and Calvert. The arrangement of the AFI promotes systematic searches for chemical analogs and assists users in locating possible matches when only partial chemical information is available. The structural indexes aid in characterization by correlations to prototype and related structures. Some applications of the indexes are given here.

Ab initio structure determination of new compound (Pb0.6Cu0.4)Sr2PrCu2O7−x was obtained at 300 and 100 K from X-ray powder diffraction data and refined by Rietveld technique. (Pb0.6Cu0.4)Sr2PrCu2O7−x has an isotypical structure with TlBa2CaCu2O7 (1212) at both 300 and 100 K. At 300 K, crystal data: (Pb0.522Cu0.4)Sr2PrCu206.53, Mr=681.293, tetragonal system, space group P4/lmmm, a = 3.8631(5)Å, c= 11.9134(2)Å, V= 177.79Å3, Z= 1, Dx, = 6.3631 g/cm3, μ=1036.549 cm−1 (λ=1.54051 Å), F(000) = 299.6, the structure was refined with 31 parameters to Rwp = 4.02%, Rp=2.96% for 3379 step intensities and Rb = 4.80%, Rf=5.17 for 143 reflections, “goodness of fit” S = 2.20. At 100 K, crystal data: (Pb0.547Cu0.4)Sr2PrCu2O6.89, Mr=692.232, tetragonal system, space group P4/mmm, a = 3.8580(2) Å, c= 11.8898(5) Å, Z=1, Dx = 6.4953 g/cm3, μ= 1053.235 cm−1 (λ=1.54051 Å), F(000) = 304.6, the structure was refined with 32 parameters to Rwp = 5.53%, Rp=4.22% for 2574 step intensities and Rb = 6.11%, Rf=5.31% for 111 reflection, “goodness of fit” S= 1.79. Moreover, the composition of Pb was refined to 0.522 at 300 K and to 0.547 at 100 K as compared with the stoichiometric composition 0.6.

Fourier transform methods of smoothing and interpolation are applied to X-ray diffraction data. It is shown that, frequently, too small a step size is used. Major gains are to be expected by selection of the optimum step size and use of these methods.

A comparison of Fourier transforms of diffractograms of quartz measured between 67 and 69° 2θ, collected at varying step intervals (0.1 to 0.01° 2θ) was used to illustrate these applications. By examining the Fourier transform of the diffractogram and noting where it decays to die baseline, a reasonable estimate of the optimal step interval can be obtained. In addition, Fourier interpolation can be used to enhance the appearance of the diffractogram, approximating a continuous plot.

Crystal data and results of structure refinements for ScPO4 are reported. The material is tetragonal, I41/amd, with a = 6.5787(2) Å, c = 5.7963(2) Å, Vd = 250.86(2) Å3, Z = 4, Dx = 3.704 Mg/m3. Intensity data were obtained from a Stoe transmission type diffractometer equipped with a position sensitive detector. CuKα1 radiation, λ = 1.5405981 Å was employed. Silicon, SRM 640b (a = 5.43094 Å) was used as an internal standard. The structure was refined by the Rietveld method by aid of three different programs.

X-ray diffraction data has been collected from biological calcific mineral associated with human bone, breast tissue, ureteric calculi, heart valve, and aorta. All the materials are shown to have a nominal calcium hydroxyapatite structure and Rietveld analysis has been performed to extract microstructural information. All refinements achieved a final Rwp value of <10%. The lattice parameter ranges are a=9.375(3)(breast)−9.4316(8)(heartvalve), c=6.866(1)(uretericcalculi) −6.899(1)(rib), and crystallite size range from 40 Å (breast) to 99 Å (ureteric calculi). A correlation between crystallite size estimates from this Rietveld analysis and line profile methods is demonstrated. The results are supported by an infrared study and previous data from alternative techniques. Thus, it is demonstrated that the microstructure of these materials may be characterised by application of the Rietveld method.

The title compound was synthesized by high temperature reaction of the component elements. This phase, formerly classified in the group of Nowotny phases, crystallizes in the hexagonal system with space group P63/mcm. Crystal data and indexed X-ray powder diffraction data are reported.

The structures of the solid solution series (Sr4−δCaδ)PtO6, with δ=0, 0.85(1), 2, and 3, have been investigated using the Rietveld refinement technique with laboratory X-ray powder diffraction data. A complete solid solution between Sr and Ca was confirmed to exist. These compounds crystallize in the rhombohedral space group R3¯c. The cell parameters of the series range from a of 9.4780(3) to 9.7477(1) Å, and c from 11.3301(4) to 11.8791(1) Å for δ from 3 to 0, respectively. The structure consists of chains of alternating trigonal prismatic (Sr, Ca)O6 and octahedral PtO6 units running parallel to the c axis. These chains are connected to each other via a second type of (Sr, Ca) ions, which are surrounded by eight oxygens, in a distorted square antiprismatic geometry. As Ca replaced Sr in Sr4PtO6, it was found to substitute preferentially in the smaller octahedral (Sr, Ca)1 site (6a) rather than at the eight-coordinate (Sr, Ca)2 site (18e). There appears to be an anomaly of cell parameters a and c at the compound Sr3.15Ca0.85PtO6. Their dependence on Ca content changes at δ≈1.00, where the Ca has fully replaced Sr in the 6a site. The substitution of Sr by Ca reduced the average (Sr, Ca)1–O length from 2.411 to 2.311 Å and (Sr, Ca)2–O from 2.659 to 2.570 Å as the composition varied from Sr4PtO6 to SrCa3PtO6. Reference X-ray powder diffraction patterns were prepared from the Rietveld refinement results for these members of the solid solution series. Magnetic susceptibility measurements of three of the samples (δ=0, 0.85, 2) show electronic transitions at low temperatures.

Internal elastic strain (i.e., residual stress) and the diffracted X-ray intensity variation over several orientations of crystallites with respect to the specimen surface were investigated as a means of differentiating two qualities of polycrystalline nickel plating. A unique instrument based upon a position-sensitive scintillation X-ray detector was used to apply all of the techniques commonly applied to X-ray stress analysis in this investigation. It was concluded that residual stress measurements did not provide a clear distinction between the two specimens, but comparison of the relative intensities diffracted from crystallographic planes at certain orientations with the surface did provide a distinction.

Because of their potential to induce a number of pathological diseases and their widespread industrial usage in the past, the fibrous minerals forming asbestos have been the subject of a number of studies in the past. Although quantification of asbestos minerals by optical and electron microscopy (SEM, TEM) is a routine technique in the case of dispersed airborn fibers, the detection and the quantification of small amount of fibrous minerals like chrysotile in bulk materials such as building materials is exceedingly difficult. A method for the detection and evaluation of asbestos minerals in massive samples is described, based on a combination of Rietveld and RIR (Reference Intensity Ratio) methods. Lower detection limits are about 0.5-1.0 wt % for chrysotile, depending on powder pattern, counting statistics, and matrix absorption. The chrysotile wt % determined on powder diffraction profiles collected on a conventional instrument is precise to about 1.0 wt % absolute (relative error in the range 0-10%). The technique is of straightforward application. If compared with the commonly used microscopic or spectroscopic techniques, it is of much advantage from the point of view of time, and the results are more accurate and statistically significant of the bulk material. A model for the cylindrically disordered structure of fibrous chrysotile is especially developed for the simulation of the X-ray powder patterns, and it is proposed here.