Precision X-ray powder-diffraction data of pure solid C70 is reported. C70 prepared by slow evaporation of C70-in-toluene solution adopts an hcp structure (space group P63/mmc) with lattice parameters a=10.5934(10)Å and c=17.262(2)Å.

An experimental investigation has been carried out to determine the extent to which axial divergence in a conventional powder diffractometer influences the measurement of peak profile parameters. A Siemens D5000 θ–2θ diffractometer was used for this study along with the LaB6 line profile standard SRM 660. Eight unique levels of axial divergence were investigated either by removing one or more of the Soller slits, or by introducing different combinations of Soller slits in the incident and diffracted beams. The measure of axial divergence used throughout is based on the maximum axial divergences of the incident and diffracted beams, Ψi and Ψd. Axial divergence produces a small and almost constant shift δ2θp in the peak angle which in a typical diffractometer would amount to a zero offset 2θ≈0.005°. The integrated intensity of a profile increases almost linearly with the product Ψi*Ψd. The increase in breadth in profiles in the angular region 2θ<120° arises mainly from the change in asymmetry DH=Hlo−Hhi in which one side of the profile broadens (i.e., either the high angle or low angle side) without any significant broadening of the other side. Moreover, the asymmetry DH is linearly dependent on 2θ for a fixed level of axial divergence, and linearly dependent on the total axial divergence Ψi+Ψd at fixed 2θ.

Crystals of green to bluish green rosasite from Tsumeb, Namibia are monoclinic, space group P21/a, with refined unit-cell parameters a = 12.873 (3), b = 9.354 (3), c = 3.156 (2) A, β = 110.36 (3)°, V = 356.3 (5) A3 and a:b:c = 1.3762:1:0.3374, with Z = 4 and Dx = 4.15 g./cm.3. Crystals are twinned by 180° rotation about a*. A fully indexed powder pattern is presented. Electron-microprobe analyses, average (wt. %): Cu 32.9, Zn 23.7; this suggests an analytical formula of (Cu1·18 Zn0·82) (CO3) (OH)2. The rosasite is optically biaxial negative, α = 1.673 (1), β = 1.796 (3), γ = 1.811 (3), 2Vx = 33 (5)° (calc. 36.4°), with X = c, Y = a* and Z = b.

Rietveld analysis has been successfully used to characterize plasma-sprayed PSZ coatings in a study of the structural stability of 8 wt. % Y2O3–ZrO2 powders and 23 wt. % CeO2/3 wt. % Y2O3–ZrO2, sprayed onto steel substrates. The ceramics were examined in powder form prior to spraying, as-sprayed and after a series of high-temperature soaks at temperatures relevant to those found in heat engines. The study showed that the Y2O3–ZrO2 powders consist of mixtures of the cubic (as the minor phase) and tetragonal (major phase) zirconia and the cubic zirconia polymorph, whereas the as-sprayed materials contain only the tetragonal (major phase) and monoclinic polymorphs indicating that the cubic phase has been lost by transformation. The CeO2–ZrO2 powders consist of a mixture of cubic, tetragonal (major), and monoclinic polymorphs of which the monoclinic phase disappears after plasma spraying. After extended thermal cycling, the Y2O3–ZrO2 coatings did not alter in phase composition whereas the CeO2–ZrO2 coatings became entirely tetragonal.

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.

Wolfeite (Fe0.59Mn0.40Mg0.01)2PO4(OH) from the Hagendorf-Sud pegmatite, Bavaria, Federal Republic of Germany, yields unit-cell parameters of: a = 12.319(1), b = 13.280(2), c = 9.840(1) Å and β = 108° 24(1). Dmeas. = 3.82(2); Dcalc. = 3.88. An indexed powder diffraction pattern is given.

An indexed X-ray powder diffraction pattern is reported for Ca4A6O12SO4, prepared by solid state reaction. The compound crystallizes in the tetragonal system with a = 13.031(3) and c = 9.164(2) Å, V = 1556.1 (8) Å3, Z = 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 ammonium copper molybdates having the stoichiometric compositions (NH4)2Cu(MoO4)2(NH3)2 and (NH4)2Cu(MoO4)2 have been synthesized from aqueous solutions. The compounds crystallize in the triclinic system with space group . Crystal data and indexed X-ray powder diffraction data are reported for both phases.

An X-ray detector chain consisting of a Xe-filled proportional detector followed by a pulse height analyzer tuned to 8.1 keV may register energies between 5 and 45 keV, although with a low efficiency at the edges. For diffraction experiments on single-crystalline substrates, these diffracted intensities can be significant. In the high-energy range, regions of even higher intensity are found due to the so-called escape process. In the diffraction angle scan of an (001) oriented Si single-crystal measured with a low (fixed) incidence angle, we have identified 21 peaks, originating from three different diffraction processes: diffraction from white radiation, diffraction observed via an escape process, and crystal truncation rod scattering. These peaks interfere with diffraction studies if such a single crystal is used as a substrate for polycrystalline samples. A great reduction in the substrate background and removal of most of the substrate diffraction peaks is achieved with a graphite monochromator or with a graphite monochromator together with a β-filter.

Diffraction peak broadening analyses were carried out on diffraction profiles of several reflections from hot-pressed α-Al2O3 containing 29, 18 and 10 volume % β-SiC whiskers. The data were analyzed and compared using four different integral breadth methods for microstrain and crystalline size. All four methods gave comparable results, within an order of magnitude, for the microstrains in each phase: (2-15 × 10−4 for the matrix and (6-19 × 10−4 for the whiskers). Microstrains in both matrix and whiskers decreased with decreasing volume % of whiskers for all four methods. Trends in the crystallite size were less consistent but for the matgrix, an incrfease from ∼665 to 1565Å was found with decreasing whisker content using DeKeijser's method.