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 “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.

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.

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.

The solid solutions Y2−xDyxO3 (x=0.20,0.50,0.74,1.40,1.80) were obtained by ceramic technology. The crystal structures were refined from X-ray and neutron diffraction data measurements in the cubic space group Ia3 by the Rietveld method. The unit cell dimensions varied from 10.6056(4) Å to 10.6624(1) Å. The structure characteristics were analyzed in relation to the concentration of the magnetic ion. The selected cation–anion–cation bonds, important for the understanding of the superexchange interaction and the magnetic properties, are given. In all samples the Dy3+ ions are randomly distributed in the cation sites 8(b) and 24(d). Comparing the random cation distribution in Y2−xDyxO3 and the preferential distribution in Y2−xGdxO3, it has been concluded that the type of distribution depends on the difference of the lattice constants between RE2O3 and Y2O3. Hence, in this cubic Mn2O3-type of structure, a preferential distribution can be expected in Y2−xNdxO3, Y2−xSmxO3, Y2−xEuxO3, Y2−xLuxO3, and a random distribution in Y2−xHoxO3.

X-ray powder diffraction data for chioroquine sulphate monohydrate [7—chloro—4—(4—diethylamino—1—methylbutylamino)—quinoline sulphate monohydrate, C18H26C1N3· H2SO4 · H2O] have been determined. Crystals of chioroquine sulphate monohydrate are orthorhombic, space group P212121 with a=9.0134(7), b=11.7417(6), c= 19.850(1) Å, Z=4, and Dx= 1.378 g cm−3. The F30 index is 121 (0.0062, 40).

Surface roughness of planar samples causes an additional attenuation of X-ray diffraction intensity measured in Bragg–Brentano geometry. The decrease of intensity becomes stronger with decreasing scattering angle. This is part of the microabsorption effect. Two quantitative expressions describing the microabsorption effect are incorporated into the DBWS 9006-PC Rietveid program [D. B. Wiles and R. A. Young, J. Appl. Crystallogr. 15, 149–151 (1981)]. The procedure is applied to scattering data obtained from YBa2Cu3O7-powder samples with different degree of surface roughness but approximately identical bulk structure. The procedure is proved to work well. However, the values obtained for the parameters of the temperature factors and the microabsorption effect are correlated, and careful discussion is necessary to interpret the results.

A task group of the JCPDS—International Centre for Diffraction Data (ICDD) was established for the purpose of investigating a methodology which would be applicable for statistical process control monitoring of X-ray powder diffractometers. A procedure for collecting X-ray diffraction data for statistical process control purposes and the incorporation of these data into control charts are presented. The results of this task group show that, through the use of statistical process control methods, noncontrol situations for diffractometers were detected, the causes of these problems were identified, and these problems were corrected and noted on control charts.

The multicomponent Rietveld profile refinement technique for powder neutron diffraction patterns has been applied to arrive at a quantitative phase analysis of crystalline Ce2Fe17 and α-Fe impurity in a powder specimen of Ce2Fe17.

Powder diffraction data for semiconductor and metallic states of vanadium dioxide are presented. The structures are refined by Rietveld methods using a monoclinic cell (a = 5.7529Å, b = 4.5263Å, c = 5.3825Å, β = 122.61°) and space group P21/c for the room temperature data, and a tetragonal cell (a =4.5540Å, c = 2.8557Å) and space group P42/mnm for data collected at 400 K. The similarity between the corresponding X-ray diffraction patterns is discussed. The transition process from the monoclinic to tetragonal phase is investigated and initial evidence for the coexistence of phases over a small temperature range is presented.

The structure of pyrochlore type Y2Sn2O7 has been refined by Rietveld analysis from 1.4925 Å neutron powder diffraction data collected at 295 K and containing 46 independent reflections. The refinement figures of merit were Rp = 0.041, Rwp = 0.055, Rexp = 0.039, and RB = 0.006. The structure is a pyrochlore type, space group (S.G.) with a = 10.3723(1) Å, Dx = 6.21 g cm−3, and with the oxygen position parameter of 0.33694(5). The Sn atoms are in a nearly regular octahedral coordination whereas the Y has a distorted 8-fold coordination geometry. The anisotropic thermal parameters were also determined. The refined model has been used to calculate a set of d-I X-ray data for search/match analysis.

The X-ray powder diffraction pattern for a sample of the high-temperature superconducting phase Tl0.5Pb0.5Sr2CaCu2O6.5+δ has been determined. The sample was prepared by a molten salt technique and had a Tc of 96 K.