A new preparation procedure to obtain tetragonal pure zirconia powders is reported together with a detailed analysis of the profile of X-ray Diffraction (XRD) peaks. The crystallization kinetic up to 800°C is described through r.m.s. microstrain and crystallite size distributions. The results of two methods of profile analysis are compared. After thermal treatments up to 100°C the samples of amorphous gel prepared crystallize in the tetragonal structure. The monoclinic phase occurs only above this temperature. Moreover the tetragonal to monoclinic transformation has a strong effect in changing the shape of the distributions. Studying the crystallite size distributions we can infer a critical size of about 300 Å for the tetragonal crystallites to transform. The shape of the mean crystallite of a fully tetragonal sample is also described.

Powder X-ray diffraction has become a routine procedure for the quantification of phases in mixtures. The most common method for this measurement is the Rietveld method, which generally returns the relative weight percentages of the crystalline components within the mixture. However, in many instances, it is also desirable to obtain an estimate of the amorphous content of a sample. There are several methods that may be used for this measurement and their accuracy has been assessed previously with a number of ideal, synthetic mixtures. Many samples, especially in the mineralogy sphere, are far from ideal and contain multiple phases of varying absorption contrast. This creates a microabsorption problem which affects the accuracy of the determination of both the crystalline and amorphous components. This paper assesses commonly used methods of amorphous determination with a series of synthetic samples designed to create a considerable microabsorption problem.

A strategy for qualitative X-ray phase analysis of complex multiphase solids is illustrated through the analysis of eight fixed-bed gasification ashes. Coal from the same lignite formation was gasified in three different reactors. Despite the differences in gasifiers and their operating conditions, all of the ash specimens had the same basic crystalline phase assemblage: silicates and aluminosilicates (merwinite, dicalcium silicates, melilite, nepheline, carnegieite and a sodalite structure phase), oxides (ferrite spinels, hematite and periclase), calcite and residual lignite minerals (quartz, plagioclase). The identification strategy relied on a bulk chemical analysis of each ash and used manual methods with the JCPDS-ICDD search manuals for the Powder Diffraction File. Grain picking, size separations, magnetic enrichment, separation by hardness, dissolution of water soluble phases, and further crystallization of the ash through heat treatment all figured in the identification strategy. Identification of more than a dozen minor and trace phases resulted from these additional methods. Several trials with an automated search/match system demonstrated the difficulties of analyses of such complex phase assemblages. The need for SEM characterization of the ashes to accompany the XRD analyses is discussed.

The crystal structure of Al7O3N5 was characterized by laboratory X-ray powder diffraction (CuKα1). The title compound is trigonal with a space group R3m (centrosymmetric). The hexagonal unit-cell dimensions (Z = 3) are a = 0.305 06(1) nm, c = 5.7216(1) nm, and V = 0.461 11(2) nm3. The initial structural model was derived by the charge-flipping method and refined by the Rietveld method. The final structural model showed the positional disordering of two of the four Al sites. The maximum-entropy method-based pattern fitting method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The disordered crystal structure was successfully described by overlapping five types of domains with ordered atom arrangements. The distribution of atomic positions in one of the five types of domains can be achieved in the space group R3m. The atom arrangements in the four other domains are non-centrosymmetric with the space group R3m. Two of the four types of domains are related by a pseudo-symmetrical inversion, and the two remaining domains also have each other in the inversion pseudo-symmetry.

To enable mechanical milling of small (0.1–1.0 g) samples, a cylindrical grinding vessel machined from polypropylene and furnished with tungsten carbide rods has been designed and produced for use inside the conventional jar of a McCrone Micronizing Mill. The vessel is about one-seventh the volume of the conventional jar supplied by the manufacturer. The conditions of milling for both the conventional and the miniaturized-grinding assemblies were tested using quartz sand as a limiting case. The median grain sizes of the resultant powders were measured by an X-ray gravitational-sedimentation method, with contamination from the grinding media measured by Rietveld refinement and by instrumental neutron activation analysis. The use of tungsten carbide grinding elements permits rapid wet milling of a small sample to the same median grain size in about one-third of the time required by a regular sample ground in corundum. The relative contamination (by tungsten carbide on a weight basis) using the miniaturized-grinding assembly is about 6(1)% of the proportion of corundum contamination yielded by the conventional grinding assembly.

Techniques for estimation of element levels directly in humans (noninvasive in vivo) or in samples (in vitro) from humans are reviewed. Toxic, nonessential, trace elements may cause temporary or permanent damage to various organs and tissues in humans. There is thus a need to control the concentrations. Knowledge of the relations between toxic effects and element concentration may be extracted from measurements in humans as well as in samples from humans and her environment. Applications traditionally include occupationally exposed subjects, but an increasing research area is studies of members of the general population and of patients undergoing therapy for malignant and other diseases. Most in vivo XRF studies deal with lead in bone and cadmium in kidneys. For retired lead workers, a clear association has been demonstrated between bone lead and blood lead, due to endogenous lead excretion from the skeleton. A study of mercury in vivo showed that the technique is capable of detecting mercury in heavily exposed worker’s kidneys. In vivo XRF in cancer and rheumatology patients has helped to understand how platinum and gold are retained in the human body. The newest in vivo applications include zinc in prostate gland and arsenic in skin.

X-ray powder diffraction data for buckminsterfullerene, C60 are reported. The crystal structure is a face-centered cubic unit cell with a = 14.165 (1) Å. The reference intensity ratio (I/Icor) is 2.20.

Plant surfaces are mostly covered with microscopic layers of wax which exhibit characteristic morphologies, visible under high magnification. Waxes belonging to three different types were investigated. Powder data of seven natural and three recrystallised waxes as well as of two isolated compounds are presented. The mainly crystalline nature of the studied plant waxes is proved. The correlation between morphology, chemical composition, and powder patterns is discussed.

The systems PbO–Bi2O3–P2O5/As2O5/V2O5 have been studied with respect to their compounds and solid solutions. A number of new compounds, particularly with high-Bi contents were found. Most of them are structurally closely related to the CaF2 and δ-Bi2O3 structures. Several binary and ternary solid solutions with P/As/V substitutions were investigated.

X-ray powder data and crystal data for acetaminophen, C8H9NO2, are reported and results are compared to existing PDF patterns.

Powder X-ray diffraction data are reported for La0.6Sr0.4Co1−yFeyO3 (y=0.1, 0.25, 0.4, 0.6, 0.8, 1.0). The powders were prepared by thermal decomposition of metal-containing complex solutions. All compositions have rhombohedral unit cells. In hexagonal setting, the cell parameters are a=5.4388 Å, c=13.2355 Å for y=0.1; a=5.4427 Å, c=13.2542 Å for y=0.25; a=5.4530 Å, c=13.2838 Å for y=0.4; a=5.4769 Å, c=13.3175 Å for y=0.6; a=5.5057 Å, c=13.3918 Å for y=0.8; and a=5.5278 Å, c=13.4368 Å for y=1.0. The space group is probably R3c (167) for all compositions. The observed trends in the change of the pseudocubic cell parameter ac with increasing iron content can be explained in terms of substitution of Co4+ by Fe4+ when y<0.4, and substitution of Co3+ by Fe3+ when y≳0.4.

A mathematical model for interpreting the anisotropical broadening of the powder diffraction lines by an average crystallite in the form of a triaxial ellipsoid is developed. The model covers satisfactorily a broad range of averaged crystallite shapes in polycrystalline samples of all crystal symmetries and provides simple formulas for use in powder pattern fitting routines. When ra, rb, rc are the principal ellipsoid radii, and ca, cb, cc direction cosines of diffraction vector related to the principal axes of ellipsoid, the average dimension of crystallites along the diffraction vector (Dhkl) is: Dhkl=K/ca2/ra2+cb2/rb2+cc2/rc2. The coefficient K has the value 3/2 if Dhkl is the volume average dimension of crystallites along the diffraction vector, or 4/3 in the case of the surface average dimension. The appropriate expression for use in whole pattern fitting routines is: b11h2+b22k2+b33l2+2b12hk+2b13hl+2b23kl=K2/Lhkl2dhkl2, where bij are the elements of a second-rank symmetric tensor. Finding eigenvalues and vectors of tensor b gives dimensions and orientations of the principal ellipsoid radii in reciprocal lattice values.

Two methods may be used to measure the reference intensity ratio: (1) by measuring intensities from samples prepared by mixing the analyte and standard together in a known weight ratio and (2) measuring separately the intensities for the analyte peak and reference standard peak from pure phase preparations and by correcting the intensities with mass absorption coefficients. Both methods give identical results that are independent of the difference in mass absorption between analyte and standard. These reference intensity ratios may be universally applied to both matrix flushing and adiabatic procedures in multicomponent analysis providing that preferred orientation, microabsorption, and extinction can be eliminated or greatly minimized in the samples under analysis.

A technique to improve the stress measurement from a Debye–Scherrer ring (D–S ring) is reported. In a previous work, the authors reported a technique to calculate stress from the Fourier series of the normal strain of a D–S ring. That technique, similar to the cosα method that came before it, is inaccurate when the grain size of the specimen is relatively large. To cope with this problem, the authors propose using the oscillation of the X-ray incident angle. The present study demonstrates this technique to improve the stress measurement.

2,4,6-Trimercapto-s-triazine, trisodium salt (ideally, Na3S3C3N3·9H2O), also known as TMT-55, is a white powder that is used to precipitate heavy metals from contaminated waters. Chemical analyses confirmed the nominal composition. TMT-55 crystals are uniaxial negative with indices of refraction (25 °C) of nε=1.520 and nω=1.675. The structure was determined by single-crystal methods at 25 and −110 °C. A powder pattern was determined and compared to a simulated pattern based on the 25 °C structure data. Crystal data at 25 °C are: R3;Z=6; a=17.600(1) Å and c=9.720(2) Å; V=2607.5(5) Å3; Dx=1.55 g/cm3.

Synthetic analogs of naturally occurring nanoparticles have been studied by a range of X-ray techniques to determine their structure and chemistry, and relate these to their novel chemical properties and physical behavior. ZnS nanoparticles, formed in large concentrations naturally bymicrobial action, have an interesting core-shell structure with a highly distorted and strained outer layer. The strain propagates through the particles and produces unusual stiffness but can be relieved by changing the nature of the surface ligand binding. Weaker bound ligands allow high surface distortion, but strongly bound ligands relax this structure and reduce the overall strain. Only small amounts of ligand exchange causes transformations from the strained to the relaxed state. Most remarkably, minor point contacts between strained nanoparticles also relax the strain. Fe oxyhydroxide nanoparticles appear to go through structural transformations dependent on their size and formation conditions, and display a crystallographically oriented form of aggregation at the nanoscale that alters growth kinetics. At least one Fe oxyhydroxide mineral may only be stable on the nanoscale, and nonstoichiometry observed on the hematite surface suggests that for this phase and possibly other natural metal oxides, chemistry may be size dependent. Numerous questions exist on nanominerals formed in acid mine drainage sites and by reactions at interfaces.

The General Structure and Analysis Software II (GSAS-II) package is an all-new crystallographic analysis package written to replace and extend the capabilities of the universal and widely used GSAS and EXPGUI packages. GSAS-II was described in a 2013 article, but considerable work has been completed since then. This paper describes the advances, which include: rigid body fitting and structure solution modules; improved treatment for parametric refinements and equation of state fitting; and small-angle scattering data reduction and analysis. GSAS-II offers versatile and extensible modules for import and export of data and results. Capabilities are provided for users to select any version of the code. Code documentation has reached 150 pages and 17 web-tutorials are offered.

Using the Rietveld profile method, the atomic coordinates and anisotropic temperature factors of KCaF3 were refined. At room temperature, KCaF3 crystallizes in monoclinic B21/m symmetry, with the lattice parameters: a=8.754(2) Å, b=8.765(4) Å, c=8.760(5) Å, β=90.48(3)°, V=672.1(3) Å3, Z=8. The refinement procedure was stopped when RB=0.05 and the Durbin–Watson statistic factor=0.85 had been reached. The structure determined is related to the tilting of CaF6 octahedra of the a−b+c− type, which are responsible for the monoclinic distortion in perovskite crystals.

A new Peltier-cooled solid-state Si(Li) detector has been compared to a traditional scintillation detector/diffracted-beam graphite monochromator system in conventional X-ray powder diffraction applications. Parameters studied included absolute count rates, detector linearity, peak-to-background ratios, detection limits, fluorescent radiation elimination, and peak profile shapes. Comparisons were performed on a Siemens D-500 θ-2θ diffractometer using constant sample and nondetector instrumental parameters. Advantages of the Si(Li) detector include a significantly increased count rate (3.4 - 3.8 times), primarily due to the elimination of the graphite monochromator, slightly lower background count rates, and the ability to change the analysis energy quickly. The higher count rate and slightly lower background count rate of the Si(Li) detector allow collection of data more rapidly than possible with a scintillation detector/diffracted-beam monochromator system and yield improved peak-to-background ratios and detection limits. Significant disadvantages of the Si(Li) detector include pronounced deviation from linearity at low count rates, making accurate measurement of even moderate countrate peaks difficult, and detector shutdown due to 100% deadtime between 4 and 5 × 10 4 counts/s (cps). The Si(Li) detector and the scintillation detector/diffracted-beam monochromator system are comparable in terms of fluorescence radiation elimination, resolution, and peak shape, although it appears tfiat die diffracted-beam monochromator measurably reduces the low-angle portion of the half width of all reflections.

Nanocrystalline anatase powders synthesised by various chemical processes as super/subcritical fluid extraction, sol-gel technique and hydrolysis of titanium alkoxides in hydrogen peroxide were studied by X-ray diffraction (XRD) whole profile modelling method (WPPM) in order to reveal correlations between structural and micro-structural parameters as well as sample treatment conditions. Anisotropy of the diffraction line broadening due to truncated bipyramidal shape of anatase crystals was discussed. The hkl-anisotropy can be very strong but also almost negligible in dependence on relative ratio of the crystallite dimensions. The latter was the case for the studied samples. The size of synthesised anatase nanoparticles was within the range 3–25 nm. The theoretical total surface area of crystallites calculated from XRD was in a good correlation with the surface area measured by the nitrogen physisorption up to the temperature 400–450 °C, when the particles started to agglomerate. At atomic scale a unit cell volume contraction with decreasing crystallite size and a significant deficiency in the Ti-site occupancy was observed. Both effects were attributed to the presence of Ti-vacancies and a linear coefficient between the relative cell volume contraction and the fraction of Ti-vacancies was estimated to (–0.017 ± 0.003).