The crystal structure of the mullite in a commercial material was refined by the Rietveld method using laboratory X-ray powder diffraction data. In this one refinement, most of the common challenges—including variable stoichiometry (partially occupied sites), multiple impurity phases, amorphous material, constraints, restraints, correlation, anisotropic profiles, microabsorption, and contamination during grinding—are encountered and the thought processes during the refinement are described step-by-step. Interpretation of the refinements includes bulk chemical analysis, chemical composition of the mullite, assessment of the geometry, bond valence sums, the displacement coefficients, crystallite size and microstrain, comparison to similar structures to assess chemical reasonableness, and the nature of the amorphous phase.

A specially designed specimen holder employing a beryllium dome has been fabricated for collection of X-ray diffraction (XRD) data from highly reactive materials. The specimen holder has a robust O-ring type seal (<10−9Torr) and no observed intensity artifacts in the 1° to 150° 2θ range. The design also minimizes specimen displacement errors and allows for analysis of both powders and bulk specimens (i.e., pellets). The simple design makes for straightforward assembly of the holder within the confines of a glove box. XRD analysis of hygroscopic LaBr3 powders collected with this holder are suitable for Rietveld structure refinement, yielding unit cell lattice parameters of a=7.9703(6) Å and c=4.5122(6) Å; cell volume=248.44(6) Å3; Rp=7.70%.

The evolution of internal stresses in oxide scales growing on polycrystalline Fe3Al alloy in atmospheric air at 700 °C was determined using in situ energy-dispersive synchrotron X-ray diffraction. Ex situ texture analyses were performed after 5 h of oxidation at 700 °C. Under these conditions, the oxide-scale thickness, as determined by X-ray photoelectron spectroscopy, lies between 80 and 100 nm. The main phase present in the oxide scales is α-Al2O3, with minor quantities of metastable θ-Al2O3 detected in the first minutes of oxidation, as well as α-Fe2O3. α-Al2O3 grows with a weak (0001) fiber texture in the normal direction. During the initial stages of oxidation the scale develops, increasing levels of compressive stresses which later evolve to a steady state condition situated around −300 MPa.

X-ray powder diffraction data, unit cell parameters, and space group for alaptide are presented (a=21.136(4) Å, b=7.212(4) Å, c=6.126(3) Å, space group P212121, cell volume=933.8(8) Å3, and Z=4). All measured lines were indexed and are consistent with the P212121 space group. No detectable impurities were observed.

K2Zn3(P2O7)2 was synthesized by solid state reaction and its crystal structure was determined by ab initio method from powder X-ray diffraction (XRD) data. The title compound was determined to be orthorhombic with space group P212121, Z=4, and lattice parameters a=12.901(8) Å, b=10.102(6) Å, and c=9.958(1) Å. Values of lattice parameters from 303 to 573 K were measured by temperature-dependent XRD. Thermal expansion coefficients α0, lattice parameters, and cell volume at 0 K were determined to be α0(a)=1.62327×10−4/K, a0=12.855(4) Å, α0(b)=1.17921×10−4/K, b0=10.070(8) Å, α0(c)=2.62364×10−4/K, c0=9.880(4) Å, and α0(V)=6.599×10−2/K, V0=1278.967(0) Å3. The specific heat equation as a function of temperature was determined to be Cp=0.77115+0.00231T−1241.60027T−2−1.4133×10−6T2 (J/K g), for temperatures from 198 to 710 K. The melting point estimated from the μ-DTA heating curve is 795 °C.

CaMnO3 is a parent compound for numerous multicomponent manganese perovskite oxides. Its crystallographic data are of primary importance in the science and technology of functional CaMnO3-based materials. In the present study, data were collected for a CaMnO3 sample at 302 K. The crystal structure refinement yields accurate absolute values of lattice parameters, a=5.281 59(4) Å, b=7.457 30(4) Å, and c=5.267 48(4) Å, leading to orthorhombic distortion of (c/a, √2c/b)=(0.997 33,0.998 95). The orthorhombic distortion of the CaMnO3 structure is discussed on the basis of comparison of our unit-cell size with data already published. At a graphical representation of the distortion, it is observed that there is a considerable scatter of the distortion values among the literature data but, interestingly, a considerable fraction of experimental results (including the present one) for stoichiometric samples are grouped around the distortion (c/a, √2c/b)=(0.9973,0.9990), which lies close to a maximum in the extent of orthorhombicity. The influence of off-stoichiometry on the orthorhombic distortion is discussed on the basis of available experimental data. Simulations, employing a mean-field approach for low temperatures, predict an increase in cell volume and structural distortions with the concentration of oxygen vacancies when the additional electrons are localized on the manganese. A simple model of delocalization produced the opposite effect, which is expected to combine with lattice vibrations to recover the cubic phase at high temperatures.

Dislocation model of strain anisotropy is presented. The dislocation theorem of strain broadening is suggested which means that strain broadening can only be caused by dislocation-type lattice defects. Based on this theorem strain anisotropy is modeled and accounted for by assuming that strain broadening is caused by dislocations or dislocation-type lattice defects. The effect of strain anisotropy is summarized in hkl dependent dislocation contrast factors, which can be either averaged over the permutations of hkl indices or are different for each different reflection. The dislocation model of strain anisotropy provides a powerful tool to analyze slip activity, Burgers vector populations, and plasticity on the basis of line profile analysis.

The solvent-free conversion of N-carbamoyl-L-proline to hydantoin-L-proline by direct heating at 470 K is reported. A reaction mechanism is proposed based on a nucleophilic intramolecular substitution reaction involving both the lone pair of the NH2 group and the carboxylic acid group of the N-carbamoyl-L-proline. The DSC and TGA experiments show rising of the baselines of the curves prior to melting and decomposition given evidence of the onset of the thermal reaction. NMR experiments were used to identify the product of the reaction, hydantoin-L-proline, whose crystal structure was obtained from X-ray synchrotron powder diffraction data collected on the solidified melt. This compound displays a crystal packing directed by hydrogen bonds forming a layered structure pile up along the c direction.

A new ternary compound Al0.35GdGe2 has been synthesized and studied by means of X-ray powder diffraction technique. The ternary compound Al0.35GdGe2 crystallizes in the orthorhombicwith the CeNiSi2 structure type (space group Cmcm, a=4.0874(2) Å, b=16.1499(5) Å,c=3.9372(1) Å, Z=4, and Dcalc=8.007 g/cm3).

Powder diffraction experiments performed as a function of external variables like, e.g., temperature, pressure, or time open possibilities to gain additional information about the physical and chemical properties of the system under study. Sensible extraction of such information directly from in situ experiments requires the treatment of the dataset with methods like sequential and/or parametric refinements. We are progressing towards the development of the parametric refinement method, which performs simultaneous phase refinements of in situ powder patterns by imposing several rational physical models of the evolving parameters on the calculated powder diffraction profiles. One of the fundamental prerequisites for this method is that the powder patterns in the in situ dataset be grouped to their relevant phases. In this paper, we present an analytical method which uses the Pearson’s correlations coefficients of the powder patterns to automatically determine the phase transition points of the in situ powder dataset. The phase transition points determined are used to group the powder patterns belonging to identical phases and to prepare the patterns for automated sequential phase refinements. The proposed algorithm is implemented as an automated module in the multi powder diffraction pattern, data reduction software Powder 3D.

Laboratory X-ray powder diffraction was used to investigate mineralogical compositions of green pigments labeled by suppliers as “green earths.” It was found that glauconite and celadonite—minerals historically considered as the main ingredient of this pigment—were present only in Bohemian green earth, green earth from Thuringen (glauconite), and Bavarian green earth (celadonite). Other investigated pigments consist of mineralogical-component minerals with added synthetic organic colorants. The obtained results may be useful for scientists, restorers, and artists in proper choices of the pigments they use in their works.

One of the advantages of a multidetector neutron time-of-flight diffractometer such as the high pressure preferred orientation diffractometer (HIPPO) at the Los Alamos Neutron Science Center is the capability to measure efficiently preferred orientation of bulk materials. A routine experimental method for measurements, both at ambient conditions, as well as high or low temperatures, has been established. However, only recently has the complex data analysis been streamlined to make it straightforward for a noninitiated user. Here, we describe the Rietveld texture analysis of HIPPO data with the computer code Materials Analysis Using Diffraction (MAUD) as a step-by-step procedure and illustrate it with a metamorphic quartz rock. Postprocessing of the results is described and neutron diffraction results are compared with electron backscatter diffraction measurements on the same sample.

Ternary Al–Cu–Ir phases, isostructural to the Al–Cu–Rh ω and C2 phases, were found to be around the Al70Cu20Ir10 and Al60Cu15Ir25 compositions, respectively. Using powder X-ray diffraction, the former was found to have a tetragonal structure (space group P4/mnc) with a=6.4142(9) Å and c=14.842(4) Å, and the latter has a cubic structure (space group Fm3) with a=15.3928(6) Å.