An Sb3Nb3O13 [Sb(III)2Sb(v)Nb(v)3O13] phase having a defect pyrochlore structure has been prepared by heating a sol–gel derived powder in oxygen. X-ray powder diffraction results indicate that Sb3Nb3O13 has a face-centered cubic structure, S.G. Fd3m(227), with a refined unit cell parameter a =10.4965(1) Å, calculated density Dx=4.893, four molecules per unit cell (Z), and a calculated figure of merit SS/FOM F30=92.4(0.009,38).

Indexed X-ray powder diffraction data are reported for two organic salts with carbon rings having two quaternary nitrogens: diazonia-6,9 dispiro [5.2.5.2] hexadecane and diazonia-6,9 dispiro [5.2.5.3] heptadecane diiodides. For these compounds, which give solid electrolytes when associated with AgI, powder diffraction diagrams calculated by the Rietveld method from single crystal structure determinations are presented and are compared to the experimental diffraction data.

This paper presents the first Table of RIR values for quantitative analysis as a model for regular updates which will appear in future issues. Diffractionists interested in the reference intensity method of quantitative analysis are urged to read the criteria for preparing data to continue this Table and then to submit new data.

Powder diffraction data were collected for a synthetic zinc molybdate of composition Na(OH)Zn2(MoO4)2·2.5H2O. The material is monoclinic, space group C2/m, with a=9.4543(12), b=6.3492(7), c=7.6453(11), β=115.899(13), and V=412.83 Å3.

XRF and XRD measurements made on a single pressed powder briquet can be combined to give more quantitative information than either technique employed alone. Speed of analysis and simplification of sample preparation are also enhanced. The algorithm presented here uses multiple linear regression of the concentrations of one or more elements on the corrected X-ray diffraction intensities of the phases containing them. The data reduction program runs on a microcomputer. Data are presented to show its application to mineralogical analysis of artificial mixtures of quartz, microcline (a feldspar) and calcite.

(Na0.6H0.4)(Ta0.7Nb0.3)O3 was synthesized by heating a tantalum/niobium scale containing two sodium tantalate/niobate phases :Na14(Ta0.7Nb0.3)12O37·31H2O and NaH2Ta0.7Nb0.3O4. Powder X-ray diffraction data for (Na0.6H0.4)(Ta0.7Nb0.3)O3 indicated it to be a cubic perovskite (ABO3/ReO3 type structure) with unit cell a0=3.894 Å. The compound is analogous to the mineral lueshite (NaNbO3), and to the high temperature forms of NaTaO3 and NaNbO3. Powder diffraction data for (Na0.6H0.4)(Ta0.7Nb0.3)O3 will be useful in the analysis of synthetic tantalum/niobium concentrates.

More than 10 000 inorganic structures based on both X-ray and neutron powder diffraction data were extracted from the ICSD database and analyzed considering overall trends, cell symmetries, occurrence of the space groups, complexity, precision and reliability of reported data. It was found that the major amount of structures belong to higher symmetries and have 2–5 atoms in the asymmetric unit. Less than 35% of the e.s.d.'s of atomic coordinates is ≤10−3 and 10−4 or better was reached in only 5% of cases. Approximately one-quarter of papers contain possibly inaccurate atomic coordinates or interatomic distances. A short review of journals publishing structures derived from powders is also given.

Occasional gaps in diffraction arcs are to be expected on “powder films” obtained with the Gandolfi X-ray camera, particularly when the specimen is a single crystal of low symmetry. The geometrical limitations of the method were succinctly and elegantly stated by the worker whose name the camera bears, in work published a quarter of a century ago. Gandolfi also stated a meansibr amelioration of the missing reflections “problem” Numerous authors have made reference to such discrepancies in the intervening period. These minor difficulties notwithstanding, the Gandolfi camera remains a powerful tool for materials analysis.

A novel algorithm has been developed for obtaining directly the applicable indices hkl for any interplanar spacing, dobs±Δdobs, of a triclinic phase with known unit cell parameters. This method is particularly useful for indexing back reflections for triclinic phases with unit cell volumes greater than 500 Å3.

The compound DyNiSn has been studied by X-ray powder diffraction. The X-ray diffraction patterns for this compound at room temperature are reported. DyNiSn is orthorhombic with lattice parameters a=7.1018(1) Å, b=7.6599(2) Å, c=4.4461(2) Å, space group Pna21 and 4 formula units of DyNiSn in unit cell. The Smith and Snyder Figure-of-Merit F30 for this powder pattern is 26.7(0.0178,63).

An improved backloading method to determine the reference intensity ratios of sedimentary minerals is presented. More than 50 reference intensity ratios of more than ten types of minerals formed in typical sedimentary environments were measured. Quantitative tests were performed on those minerals. Comparison of the results show that this method minimizes preferred orientation and improves quantitative precision (absolute deviation is less than 3%) so that it is an acceptable specimen loading method.

An increasingly frequent used sample holder, the zero-background holder (ZBH), is evaluated for use in external standard calibration of powder patterns. The effectiveness of the ZBH calibration method is determined by comparison to the conventional internal- and external-standard calibration techniques. The three calibration methods are compared using the results of lattice parameter refinements of test powders, using Si as the standard. Several test materials were used in the evaluation which cover a wide range of absorption coefficients so sample transparency effects can be distinguished from sample displacement effects. Results of the calibrations clearly indicate that the ZBH method gives precision and accuracy comparable to the internal-standard method, and significantly better than the external-standard technique. In addition, the ZBH method yields substantially better results than the internal-standard method for materials with low absorption coefficients. Low-angle calibrations are also made on a ZBH using a proposed standard, silver behenate, which has peaks from 1.5° to 20° 2θ. These calibrations have shown that if care is not taken to establish a monolayer of powder on the ZBH crystal, significant errors in refined lattice parameters will result.

X-ray powder diffraction and optical data are presented for alkali-deficient schorls from two tourmaline-dumortierite deposits. The compositions of both schorls reflect the presence of an alkali-defect substitution, whereby the alkali cation deficiencies in the crystal structure are charge balanced by trivalent for divalent cation substitutions in the octahedral sites. Refined unit cell and optical data are as follows: a = 15.9523(15), c = 7.1466(2) Å, F30 = 104(0.009, 32), M20= 68, ε = 1.638(2), ω = 1.660(2), Dx= 3.12 for the schorl from Jack Creek, near Basin, Montana, U.S.A. and a = 15.9800 (15), c = 7.1504(2) Å, F30= 156(0.006, 32), M20= 152, ε = 1.642(2), ω = 1.668(2), Dx= 3.17 for the schorl from Ben Lomond, Hervey Range, North Queensland, Australia. Indexed X-ray powder diffraction patterns are also presented.