Measurements of X-ray diffraction patterns of high-Tc superconductor and tungsten–carbide powder samples using a Bragg–Brentano diffractometer showed systematic variations of the intensities for different preparation conditions. For specimens with high surface roughness, an angle-dependent decrease of the intensities is observed which is caused by the microabsorption of the X-rays due to the microstructure of the powder sample. In Rietveld analysis, the thermal parameters are strongly influenced by this effect and may tend to negative values. A realistic description of the surface structure of flat powder samples is proposed. Using an analytical approximation for the microabsorption effect and its dependence on the microstructural parameters the Rietveld refinement yields reasonable values for the thermal parameters.

An X-ray diffraction peak-broadening analysis of four oxides is described: La2CuO4 and La1.85M0.15CuO4 (M = Ca,Ba,Sr) high-Tc superconductors. The diffraction line profiles were fitted with a convolution of specimen and instrumental functions, and the specimen peakbroadening angular dependence was analyzed with the Warren-Averbach method. It was found that microstrains and incoherently diffracting domains 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 symmetry.

By methods of X-ray structure analysis commensurate (one dimensional) and incommensurate (three-dimensional) modulations of the lazurite structure from Baikal deposits are considered. The analysis of the X-ray diffraction powder and single crystal data showed that the one-dimensional (anisotropic) modulation deforms the lazurite cubic structure and is manifested in a broadening and splitting of sublattice lines on the powder diffraction pattern of the mineral. At a three-dimensional modulation, the cubic structure is maintained. It is concluded that a density modulation is a cause of the incommensurate modulation of the lazurite structure. Due to this arrangement, a crystallographic equivalency of subcells is maintained. The cause of the commensurate modulation is an ordered distribution of intraframework units and the displacement modulation where all atoms of the mineral structure participate.

The calculated XRD profiles of alite (impure Ca3SiO5, the major phase in Portland cement) derived from seven postulated crystal structures for alite were compared with a measured alite profile, extracted from the XRD pattern of a standard Portland cement. Only two of these profiles were found suitable for multiphase Rietveld phase quantification, namely those given by the monoclinic superlattice and triclinic models. These, however, gave very slow computing times because the large low-symmetry structures generated many X-ray reflections over the pattern. Also tested was an “observed” standard profile for alite, derived from experimental alite profiles, and generated using the (hkl) file feature of the SIROQUANT P.C. quantitative analysis system. This file was based on rhombohedral pseudosymmetry and contained very few (hkl) reflections, compared to the low-symmetry models (64 reflections instead of 951 for the monoclinic and 1691 for the triclinic models, respectively). The latter standard profile gave the best fit to the known phase concentrations and gave computing times which were shorter by factors of 2.5 and 4.9 than those for the monoclinic and triclinic standard profiles, respectively.

The “standardless” quantitative phase analysis method proposed by Rius, Plana, and Planques [J. Appl. Cryst. 20, 457 (1987)] was evaluated by applying it to two series of artificial samples. The method was then applied to determine quantitatively the phases present in six different natural kaolin samples from Egypt. Two kaolinite peaks were selected for this analysis: One of them is known to be affected by stacking disorder, the other one is the 001 basal reflection, which is not significantly affected by stacking disorder. The method was also applied to samples of different mesh sizes. The results obtained when using the basal reflection showed that Egyptian kaolin is mainly kaolinite (82%–95%) together with anatase (2%–9%), rutile (1%–6%), and quartz (0.5%–7%). These analyses agreed very well with those obtained by chemical analysis. On the other hand, the analyses of the phases obtained from the peak which is strongly affected by stacking disorder were totally different. It was found also that by decreasing the particle sizes of kaolin samples the phase abundance of kaolinite increases, whereas those of quartz and anatase decrease. The results showed also that the standardless method is only applicable to peaks that are not strongly affected by structural disorder.

The analysis of crystalline organic phases by X-ray powder diffraction presents special problems, beyond those typically associated with inorganic materials. The large unit cells often associated with organic compounds, combined with the low symmetry of the structures, give rather complicated diffraction patterns that contain many low angle lines. The Bragg–Brentano geometric arrangement employed in most commercial diffractometers gives maximum (d-spacing error at low diffraction angles. This geometry, in turn, means that not only can the large (d-spacing data be of poor quality, but also that much of the low angle data required for the indexing of the pattern is subject to large errors.

The correct formulas for geometrical factors for correction of diffracted intensities in Seemann-Bohlin diffractometry were tested. A Huber 653 goniometer, gold and titanium nitride layers, white tin, and rutile as specimens were used in the reflection mode. A Huber 642 goniometer and olivine as a specimen were used in the transmission mode. It was found that, due to a variable specimen-detector distance during 2θ scan, the variable efficiency of the Soller slits in the diffracted beam must be taken into account. The model describing this effect analytically is presented. As a final test the structures of white tin, rutile, and olivine were refined from the measured data corrected for different factors.

Five structurally related compounds, TlMgAsO4, TlMgPO4, TlZnAsO4, TlZnPO4, TlZnVO4, have been synthesized by solid-state reaction. Single crystals have been grown by various methods. Space group and unit-cell parameters were determined. Powder diffraction data for each phase are reported.

Line profiles of a powder diffraction pattern and the aberrations which affect the centroid and the variances of the peaks have been analyzed using the visualization in scientific computing (ViSC) systems. The constrained optimization of those aberrations has been derived from the theory developed by Wilson (1963). It allows the determination of systematic instrumental effects and gives indication of other diffraction effects related to the samples. The CuKβ radiation was used to process the experimental data directly as it is comprised of only one single wavelength.

An attachment for commercial X-ray powder diffractometers is described. The device is made of four different parts that are largely independent of each other, and can be freely interchanged or replaced, and aligned independently. It can be home-built, or modified, with high flexibility according to user requirements, and has been tested on different problems concerning high-temperature phase transitions and solid-state reactions up to 1200 °C under vacuum, under inert gas or under various oxygen partial pressures. Examples are given of possible designs of the various parts.

Complete sets of correction factors for absorption and air scattering effects in X-ray powder diffraction are reported. Both symmetrical reflection and transmission techniques are considered and boundary conditions to be tested for any given value of scattering angles are listed. This may prove particularly useful on coding computer programs for correction of raw intensity data files. Effects of interstitial volume on correction for absorption and subtraction of air scattering were investigated. For samples of high interstitial volume, like loosely packed powders or aerogels, the contribution from air trapped inside the specimen is significant and leads to expressions of the air scattering correction factors different from those commonly reported in the literature.

After regeneration, the catalyst UOP-R-62 was used for conversion of reforming benzine. The percentage of conversion benzine fraction was considerably smaller than that of the new catalyst sample. To determine the cause of catalyst deactivation, in addition to standard methods of analysis, X-ray diffraction and scanning electron microscopy were used. Real and model samples of UOP-R-62 were analysed. Real samples were prepared with the new catalyst, a used and regenerated catalyst with good activity and a deactivated catalyst. Model samples were prepared from the new catalyst by heating at 400–1100 °C in a porcelain crucible in a muffle furnace for 1 h. Prepared samples were measured in a Philips diffractometer system and examined in a scanning electron microscope. The obtained diffractometer patterns, FWHM value of the 440 reflection of γAl2O3, electron micrographs and images of emitted characteristic X-rays were mutually compared. Only the values obtained from the deactivated catalyst differed from the others. Besides reduced broadening of the 440 line the material exhibited new X-ray diffraction lines, a change in phase composition, and modifications in morphology and microstructure. These changes are an indication that overheating of individual spheres of catalyst UOP-R-62 to a temperature of 700—1100 °C or higher caused their deactivation.

Improvements of standard X-ray powder diffractograms of two Y-type hexagonal ferrites (Ba2Co2Fe12O22, Ba2Zn2Fe12O22) are reported.

The thermal decomposition of aqueous manganese nitrate has been studied under a range of experimental conditions to scientifically assess the pyrolysis processes employed by the tantalum capacitor industry. The crystalline phase and form of the manganese oxides produced are compared by X-ray diffraction and scanning electron microscopy. Those experimental conditions producing materials with the lowest resistivity are identified. The technological significance of the decomposition process is discussed and initial results from a novel pyrolysis technique are presented.

Eight phosphates and arsenates of manganese have been synthesized and examined using powder X-ray diffraction in order to update or extend the current powder diffraction data files. The studied compounds are MnPO4·H2O, MnAsO4·H2O, LiMnPO4(OH) LiMnAsO4(OH), LiMnAsO4, Mn2As2O7) MnAsO4, and Mn(PO3)3. The powder patterns have been indexed and the cell data are reported.

Near-surface triaxial strain/stress states in polycrystalline solids are required for a full tensorial treatment including all elements of the strain/stress tensor. A possible depth dependency of the strain/stress is at best observed by grazing incidence diffraction in Seemann–Bohlin geometry (SBG). The computer program SBGBBG calculates the full strain/stress tensor from X-ray diffraction data measured either in SBG or in Bragg–Brentano geometry (BBG). At present SBGBBG is applicable only on texture-free materials.