New hexafluoroniobates IV, VNbF6 and the high-temperature form of CrNbF6 have been synthesized by solid-state reaction. The former is isostructural with rhombohedral LiSbF6, space group R3¯, and the latter crystallizes with tetragonal symmetry, space group I/4mmm. Unit-cell parameters were determined: a=5.520(1) Å, c=13.987(5) Å, V=369.0(1) Å3, Z=3 for VNbF6, and a=5.5403(5) Å, c=8.453(1) Å, V=259.5(1) Å3, Z=2 for the “HT” form of CrNbF6. Powder diffraction data are reported.

X-ray diffraction experiments performed on the compounds FeIINbIVF6 and CoIINbIVF6 have shown that they crystallize in the rhombohedral system, space group R3¯ with a cationic ordering. Unit cell parameters were determined: a=5.4201(8) Å, c=14.072(2) Å, V=357.8(1) Å, Z=3 for FeNbF6, and a=5.351(2) Å, c=13.960(6) Å, V=346.2(2) Å, Z=3 for CoNbF6. Synthesis and powder diffraction data are reported.

The application of the Rietveld method to quantify mineral components of bauxite and lateritic samples was carried out in order to determine the ability of the method to obtain accurate mineralogical abundances for these materials. The method was initially applied to synthetic mixtures using both Cu and Co Kα radiations, and it was shown that Rietveld-derived data compared favourably with the weighed compositions. Application to two types of natural bauxite resulted in a high correlation between Rietveld predicted values and those calculated by proportioning peak intensities with chemical assays. The use of the whole pattern rather than selected peak intensities gives greater accuracy, confirmed by a strong correlation between derived oxide concentrations from XRF assays. Accuracy and precision were improved by the determination of isomorphous substitution of aluminum in goethite and hematite by refinement of unit cell dimensions. Importantly, the ability of the Rietveld program to successfully model several goethites with different levels of isomorphous substitution improved the correlation between predicted and calculated values. In addition, crystallinity and crystallite size that influence the reactivity of the mineral components can be derived from refined peak profiles.

The crystal structures of BaR2ZnO5, where R=La, Nd, Dy, Ho, and Y, were studied by neutron diffraction, and that of the Er analog was investigated by synchrotron X-ray diffraction. Two structure types were confirmed for this series of compounds and agreed with those reported in literature. The compounds with a smaller size of R (R=Dy, Ho, Y, and Er) are isostructural to the orthorhombic “green phase (BaY2CuO5)” compounds. The cell parameters for compounds with the R=Er to Dy range from a=7.0472(1) Å to 7.0944(1) Å, b=12.3022(1) Å to 12.3885(2) Å, and c=5.6958(1) Å to 5.7314(1) Å, respectively. R is 7-fold coordinated inside a monocapped trigonal prism. These prisms share edges to form wavelike chains parallel to the long b-axis. The Ba atoms reside in 11-fold coordinated cages. The compounds which contain a larger size R (R=La and Nd) crystallize in the tetragonal I4/mcm space group, but are not isostructural to the “brown phases” BaR2CuO5. The lattice parameters for the La and Nd analogs are a=6.9118(1) Å, c=11.6002(2) Å for BaLa2ZnO5, and a=6.7608(1) Å and c=11.5442(2) Å for BaLa2ZnO5. The structure consists of ZnO4 tetrahedral groups (instead of planar CuO4 groups as found in the brown phase) with Ba ions inserted in between. The structure can be viewed as consisting of alternate layers of Zn-Ba-O and Nd-O extending infinitely in the xy plane and perpendicular to the z-axis.

The structure of Ba7Cl2F12 has been determined ab initio from conventional X-ray powder diffraction data by the “heavy atom” method. The cell is hexagonal (space group P6¯, Z=1), with a=10.6373(2) Å and c=4.1724(2) Å. Refinement of 38 parameters by the Rietveld method, using 278 reflections, leads to cRwp=0.173, cRp=0.135, and RB=0.054. The structure has common characteristics with that of the other BaF2-rich fluorochloride, Ba12Cl5F19. In both phases Ba2+ ions lie in tricapped trigonal prisms formed by nine halide ions, and Cl− ions occupy the center of trigonal prisms of Ba2+ ions. F− ions are located in cationic tetrahedra or square pyramids.

Powder X-ray diffraction data for Ba12Cl5F19 are reported. The cell is hexagonal (space group P6¯2m, Z=1), with a=14.0856(3) Å and c=4.2733(2) Å.

The structure of Co2Al5 (hP28, P63/mmc) was refined by means of Rietveld method. The shortest Co–Al distance amounts 2.338 Å. Co2Al5 shows a homogeneity range between Co29Al71 and Co27.5Al72.5 at 1125 K. The concentration dependence of lattice parameters was also measured. The axial ratio c/a increases with increasing mole fraction of aluminum.

Four compounds in the hexafluoroniobates IV series MNbF6 (M=Ca, Mg, Cd, Zn) have been synthesized by solid-state reactions. CaNbF6, MgNbF6, and the “high temperature” form of CdNbF6 are isostructural with f.c. cubic NaSbF6 (space group Fm3m). ZnNbF6 and the room temperature form of CdNbF6 are isostructural with rhombohedral LiSbF6 (space group R3¯). Syntheses and powder diffraction data are reported.

Mass attenuation coefficient corrections, for Rietveld phase analysis with an external compositional calibration standard, may be made using Compton scattering intensities measured by X-ray fluorescence spectrometry. The method is mainly useful for Rietveld phase analysis when mixing an internal standard is impossible or undesirable. The validity of the method has been demonstrated using a suite of alumina-zirconia powders of known composition. Also presented are results for a typical application—determination of phase composition depth profiles defining the graded compositional character of an aluminium titanate/zirconia-alumina ceramic composite.

X-ray powder diffraction data for [Ni(i-prxa)2(bpy)] (1), [Ni(i-prxa)2(phen)] (2), and [Ni(i-prxa)2(tmen)] (3), where i-pr=i-C3H7, xa=S2CO−, bpy=2,2′-bipyridine, phen=1,10-phenanthroline and tmen=N, N, N′, N′-tetramethylethylenediamine, are reported. For (1): Monoclinic, P21/n, a=10.8255(1) Å, b=12.7423(1) Å, c=15.9796(1) Å, β=92.037(3)°, V=2202.9(1) Å3, Z=4, Mr=485.3, T=296 K, DX=1.463 g/cm3, Dexp=1.47 g/cm3, CuKα1=1.540 51 Å, 63 lines. For (2): Monoclinic, P21/n, a=10.7591(1) Å, b=12.8115(2) Å, c=16.1162(3) Å, β=92.39(1)°, V=2219.5(2) Å3, Z=4, Mr=509.4, T=296 K, DX=1.525 g/cm3, Dexp=1.51 g/cm3, CuKα1=1.540 51 Å, 72 lines. For (3): Orthorhombic, P212121, a=9.341(4) Å, b=15.093(8) Å, c=15.990(7) Å, V=2254(2) Å3, Z=4, Mr=445.35, T=296 K, DX=1.312 g/cm3, Dexp=1.32 g/cm3, CuKα1=1.540 51 Å, 49 lines.

Two derivatives of 4-chloro-2,2′-iminodibenzoic acid: diethyl 4-chloro-2,2′-iminodibenzoate, C18H18ClNO4, and dimethyl 4-chloro-2,2′-iminodibenzoate C16H14ClNO4, have been investigated by means of X-ray powder diffraction. The unit cell dimensions were determined from diffractometer methods, using monochromatic CuKα1 radiation, and evaluated by indexing programs. The monoclinic cell found for diethyl 4-chloro-2,2′-iminodibenzoate was a=21.332(3) Å, b=7.889(2) Å, c=10.156(2) Å, β=91.43(1)°, Z=4, space group P2 (No. 3), Pm (No. 6), or P2/m (No. 10), Dx=1.351 mg/m3. The cell found for this compound is in good agreement with the one obtained from single crystal X-ray diffractometry. The monoclinic cell found for dimethyl 4-chloro-2,2′-iminodibenzoate has the dimensions a=15.962(2) Å, b=5.151(2) Å, c=12.590(2) Å, β=98.35(1)°. Z=4, space group P2 (No. 3), Pm (No. 6), or P2/m (No. 10), Dx=2.073 mg/m3.

The crystal structure of Ba4Ti10Al2O27 has been refined in a joint Rietveld refinement using neutron and X-ray powder data. The compound crystallizes in the monoclinic space group C2/m, with a=19.7057(3), b=11.3575(2), c=9.8318(2) Å, β=109.218(1)°, and V=2077.81(5) Å3. It is isostructural to Ba4Ti10Fe2O27 and Ba4Ti11ZnO27, and consists of a complex network of corner- and edge-sharing Ti/Al octahedra. The structure can best be described based on close-packed O/Ba-O layers in an 8-layer (8L) chhcchhc sequence. Out of a total of ten Ti/Al sites, Al was found to substitute for Ti mainly in four sites, and the remaining six sites were predominantly occupied by Ti. The unit cell contents derived from the refined site occupancies are Ba16Ti40.48Al7.52O108, essentially identical to the expected Ba16Ti40Al8O108. A reference diffraction pattern of this phase is also reported.

Estimation of reference intensity ratios (ki or RIR) can be made on the basis of an atomic scattering function. Tests of regression equations for 50 compounds that predict an approximate reference intensity ratio from the easily computed scattering function have shown usefulness in multicomponent semiquantitative X-ray diffraction analysis. The method is best applied whenever only one or two minor components of a multicomponent sample have no readily measurable or calculable ki values and must be estimated. Where the difference between observed and predicted constants is large, these tests show that the ratios of true- to test-weight fractions are proportional to the corresponding ki ratios. The largest absolute errors occur whenever the ki must be predicted for components with medium weight fraction values. Estimation of ki for components of less than 10 weight percent results in only small errors in both predicted component and the other components of the sample. Where more than two components require predicted ki in a given sample, unacceptable errors for all components may result.