We have examined the barium ferrite powder X-ray diffraction patterns in the PDF using experimental and calculated diffractograms. An improved calculated diffractogram is proposed. The result indicates that the primary peak of barium ferrite is not (107) but is (114).

Search/Match methods were used to identify probable errors in the characterization of certain ruthenate compounds. It is suggested that patterns proposed for incorporation into the JCPDS-ICDD powder diffraction database be validated as original by Search/Match procedures before they are accepted.

MeT2O6 (M = Ce, Th) are monoclinic, space group P21/n (No. 14). The cell dimensions for CeTe2O6 are a = 7.0190(7), b = 11.0423(6), c = 7.3319(8)Å and β = 108.00(8)° and for ThTe2O6 cell dimensions are a = 7.1934(4), b = 11.2310(6), c = 7.4650(2) Å and β= 108.04(6)°.

In conventional multiphase Rietveld refinement, now being used for quantitative phase determination, the crystal structure of each phase needs to be known in order to generate a calculated standard pattern of the phase to be refined against the measured XRD pattern. This is a disadvantage when the structural data for a phase are imperfect or unknown and may prevent an analysis.

A method is given whereby a phase with an imperfectly known or unknown crystal structure can be included in a multiphase Rietveld refinement, with other well-characterised phases, by use of an empirical or “observed” hkl file for that phase, with the SIROQUANT software package. The amplitudes 1F(hkl)1 in the empirical hkl file of the phase generate a reference profile for it which agrees with a measured standard pattern of the phase. Methods are given for the creation and scaling of empirical or “observed” phase hkl datasets. The Rietveld variable parameters (preferred orientation, linewidth, lineshape and unit cell) are refinable in the usual way for a phase with an empirical hkl dataset.

X-ray powder data and refined cell parameters for two titanium carbonitride solid solutions are presented. Some deviations from Vegard's law were observed.

Powder diffraction patterns have been calculated for nine isostructural rhombohedral M2(SO4)3 (M = Sc, Ti, V, Cr, Fe, Ga, Y, Rh, In) phases, and for four isostructural monoclinic M2(SO4)3 (M = V, Fe, In, Tl) phases. The pattern for monoclinic Fe2(SO4)3 is the first reported for this phase. Because structure data are available only for the two Fe2(SO4)3 polymorphs, the powder patterns of the other trivalent metal sulfates were approximated using the structure data of the isostructural Fe phases with the scattering factors and previously determined cell parameters of the various metal sulfates. These calculated patterns are termed an approximation by isostruduralism.

The calculated patterns were used to evaluate reference powder data for these phases in the Powder Diffraction File (PDF). All but two of the PDF patterns were found to differ substantially from the calculated patterns in the stronger peaks used for identification, and to be missing weak peaks that may be confused for impurities during phase identification.

A more accurate X-ray diffraction pattern for the high speed steel carbide Fe3W3C is presented. This pattern includes the low angle reflections omitted from previous studies. A wider homogeneity range for the M6C carbide phase at 1200° C is suggested.

X-ray powder patterns for the phases in the CaO-SrO-PbO ternary system, along with the corresponding crystal structures, were obtained from the literature and from the Powder Diffraction File. Available XRD patterns were compared with each other and with a simulated pattern for each phase, yielding a recommended reference pattern. The simulated powder patterns presented here deal with the phases found within the (Ca,Sr)2PbO4solid solution series and are recommended for the Powder Diffraction File (PDF).

A new X-ray diffraction pattern for the compound cerium oxygen apatite, Ce4.67[SiO4]3O is suggested. The compound was prepared by the solid state reaction of the oxides, CeO2 and SiO2 and has a hexagonal crystal structure with the lattice constants a = 9.6578 Å and c = 7.1187 Å. The sample of the most recent PDF pattern 31-0336* (Visser, 1978) for this compound is believed to be contaminated with significant quantities of N owing to the fact that it was prepared by mixing Ce2O3 and Si3N4 and its very close resemblance to the pattern displayed in the PDF 33-0333 given for the cerium “nitrogen” apatite, Ce5[SiO4]3N.

Phase transitions were found with use of an in situX-ray anvil-type of apparatus with a boron annulus at pressures up to 12 GPa. The disordering of vacancies in the In sub-structure, or α→βtransition, was found in In2Te3at p > 1.9 GPa. The next transformation from the β-form into the Bi2Te3type of structure was observed in both sesquitellurides at 2.0 GPa and 5.0 GPa for In2TGe3and Ga2Te3respectively. The In2Te3metastable phase of the Bi2Te3resulted from heating up to 200° C at p > 4.0 GPa, and it remained in a normal condition on release of the pressure. The X-ray powder diffraction data of pressure-induced phases, volume changes and bulk modulus of both sesquitellurides are given. The compressibility anisotropy of the layer pressure-induced phase was observed. The mechanism of the crystal structure transformation from the face-centered cubic structure into the Bi2Te3type is proposed to be due to the displacement of atoms from the space diagonal of the cube [111] into [112]-cubic direction and the rhombohedral distortion of the angle between these directions.

Pyrolytic graphite is frequently used as a post diffraction monochromator with powder diffractometers of the Bragg-Brentano type. Curved graphite monochromators yield high intensities and suppress efficiently fluorescent radiation except from the element which is the same as the target element of the X-ray tube. They are not, however, able to separate the Kα1 line from the Kα2 component with the X-ray targets normally used in powder diffraction. Crystals with smaller mosaic spread than graphite are needed for selecting a pure Kα1 line. Commercially available crystals which are suitable for this purpose are asymmetrically cut curved quartz and germanium monochromators of the Johansson type. Experiments have been carried out in this laboratory with two quartz monochromators and one germanium monochromator.

Sodium Calcium Magnesium Silicate, Na2Ca4Mg2Si4O15, has been investigated by means of X-ray powder diffraction. Data were obtained by a conventional diffractometer. Unit cell dimensions were determined by an indexing program. A monoclinic cell was found, a = 17.884(2) Å, b = 5.3573(8) Å, c = 7.1796(8) Å, β = 112.71 (1)°; V=634.56 A3.

The cubic Al18Ti2Mg3 phase (184 atoms/unit cell, Z = 8, space group Fdm) has been fabricated by reaction hot isostatic pressing. Quantitative energy dispersive X-ray analysis showed the phase to have nearly ideal stoichiometry. Interplanar spacings and diffraction peak intensities have been determined by X-ray diffraction. The experimental data show good agreement with the pattern calculated using atomic site positional parameters for A118Cr2Mg3, confirming that A118Cr2Mg3 is the prototype for A118Ti2Mg3.

K2YZr(PO4)3and K2GdZr(PO4)3were found to have the langbeinite-type structure (K2Mg2(SO4)3). We determined the crystal structure of these compounds from powder diffraction data. They are cubic P213 (no. 198), with a = 10.3346(1)Å and a = 10.3457(3)Å respectively. The intensity values we observed and calculated are reported. Intensity measurements indicate a random distribution of Y3+(Gd3+) and Zr4+on both Mg2+sites of langbeinite.

Metal mepirizole perchlorates, M(C11H14N4O2)3 (C104)2 where M = Co(II) and Ni(II) have been investigated by means of X-ray powder diffraction. Unit cell dimensions were determined by indexing programs from diffractometer data. Refined cell parameters (monoclinic with a C-centered cell), calculated density and Z values are presented.

X-ray powder diffraction data for the complexes of glucose monohydrate with sodium bromide (C6H12O6. ½NaBr·½H2O) and sodium iodide (C6H12O6·NaI·½H2O) are reported. The crystals of both complexes are trigonal with space group P31 (No. 144). The complex with sodium bromide has a = 16.4338 (6), c = 17.623 (1)Å, V = 4121.9 Å3, Z = 18 and Dx = 1.745 cm−3. The sodium iodide complex has a = 16.5249(6), c = 17.882(1) Å, V = 4228.8 Å3, Z = 18 and Dx = 1.867 g cm−3. The Smith-Snyder FN values for these data are F30 = 59.4(0.0097,52) for the sodium bromide complex and F30 = 82.7(0.0098,37) for the sodium iodide complex.

Crystal data for p-bromoiodobenzene (pBIB) at 293 K and a powder diffraction pattern are reported. The unit cell is monoclinic with S.G. = P21/a and Z = 2. The cell parameters are: a = 16.196(6) Å, b = 5.872 (3) Å, c = 4.233 (2) Å, β = 113.86 (2)°.

The crystal structure of the high-temperature phase of Sr2ZnWO6 prepared by air quenching from 1200° C has been determined by means of X-ray powder diffraction. β-Sr2ZnWO6 belongs to the cubic system, with space group Fm3m and a lattice parameter a = 7.9266 Å at room temperature. Its measured density is Dm = 6.93g/cm3, and each unit cell contains four formula weights.

Powder data for the title compound have been published by Kwestroo and Paping (1959) (PDF 13-325) but neither unit cell nor indices were given. A diffractogram of this compound has been successfully indexed by the program TREOR (Eriksson and Westdahl, 1985) and the unit cell subsequently refined by a least squares procedure (Table 1).

The high-temperature phases Cu4In, Cu9In4(h) and Cu2In(h) cannot be retained by quenching. In contrast to this, splat-cooling specimens of these alloys yielded single phase products. Cell parameters in the range of homogeneity of these phases were measured. Powder crystal data for Cu4In(W type), Cu9In4(h) (Cu9Al4type) and Cu2In(h) (Ni2In type) are given.