The crystal structure of [Pd(NH3)4]C2O4 was determined from X-ray powder data. The crystals are triclinic with unit-cell parameters: a=7.0807(7) Å, b=7.0806(7) Å, c=3.8011(5) Å, α=91.910(1)°, β=98.665(1)°, γ=97.283(1)°, S.G.=P−1, Z=1, V=187.11 Å3. All non-hydrogen atoms were located from the Patterson map. The structure was refined by the Rietveld technique: Rp−b=6.88, Rwp=6.51, RB=2.66. The crystal structure of [Pd(NH3)4]C2O4 is built from two types of elements: [Pd(NH3)4]2+ and C2O2−4. Cations [Pd(NH3)4]2+ form columns along c with distances (Pd–Pd)=3.8011 Å. C2O2−4 anions occupy places in the middle of the unit cell between layers of [Pd(NH3)4]2+. The compound is stable up to 200 °C and then decomposes, giving Pd powder.

CuInSeTe was synthesized by the melt and anneal technique. The compound crystallized in the chalcopyrite structure having space group I4¯2d with Z=4. Complete X-ray powder diffraction data were obtained and the unit cell parameters a and c, X-ray density and u parameter were calculated. These are a=0.5987(1) nm, c=1.1979(4) nm, Dx=5.96×103kg/m3, and u=0.2498. Atomic positions in the unit cell are proposed.© 2000 International Centre for Diffraction Data.

A quantitative phase analysis often requires advanced numerical studies to determine the appropriate intensity values. In this paper the method of fitting analytical functions to the experimental profile is applied to X-ray powder diffraction patterns obtained with FeK radiation. In the present work, the authors examine some problems connected with numerical studies, especially the function describing the experimental profile. The usefulness of the α2 elimination procedure and the angular dependence FWHM are also examined.

The X-ray diffraction data for the single phase UAl4 are reported. The data were obtained with a Huber–Guinier diffractometer with MoKα1 radiation. The unit cell of UAl4 is orthorhombic (space group Imma) with lattice parameters a=4.396 Å, b=6.251 Å, and c=13.699 Å.

X-ray powder diffraction was used as an analytical technique for the solid state synthesis of selective oxidation catalysts with large surface area. Qualitative analysis was used to determine the minimum temperature at which the synthesis was complete. Quantitative diffraction was used to analyze mixtures of isomorphous antimonates. Results indicated that the final mixtures are independent of the method of preparation, i.e., mixing or impregnation.

High temperature superconducting phases in the Tl-Ca-Ba-Cu-O system are ideally represented by the formula TlmCan−1Ba2CunO2(n+1)+m, with m either 1 or 2 and n = 1 to at least 3 (Parkin et at., 1988). Each of these phases contains one or more of the nearly planar CuO2sheets common to the cuprate superconductors. A single Ca atom separates adjacent CuO2sheets (n > 1). Single or double rock salt-like Tl-O layers are separated from the Can−1CunO2nregions by single Ba-O layers. Each of the Ca-containing members of this family crystallizes in a tetgragonal unit cell, with space group 14/mmm for the m = 2 series and P4/mmm for the m = 1 series.

Despite the general interest in this family of superconductors, little has been reported about the m = 1, n = 2 member, TlCaBa2Cu2O7−δ, hereafter called 1122. This lack of work is due at least in part to the difficulty in synthesizing the pure compound (Michel et at., 1991). Additionally, technological interest has focused on members of the family with higher superconducting transition temperatures, particularly Tl2Ca2Ba2Cu3Oywith Tcup to 125 K. The critical temperature of 1122 has been reported from as low as 50 K (Hervieu et al., 1988) to as high as 103 K (Morosin et al., 1988), and at several values in between (Ganguli et al., 1988; Liang et al., 1988). Most of the samples had other superconducting phases in addition to 1122. Because of the nearly identical a axis lengths of the unit cells of the Tl-family of superconductors, syntactic intergrowths may be present in such multiphase samples.

X-ray powder diffraction data are reported for a series of isomorphous compounds of [Ln2(CrO4)3(H2O)5]·2H2O, where Ln=La, Pr, Nd, Sm, or Eu. The compounds crystallize in monoclinic space group P21/c (No: 14) with Z=4. Refined unit cell parameters and indexed powder diffraction patterns are given.

A FORTRAN 77 program to perform full matrix least-squares refinement of unit cell parameters from powder diffraction patterns showing incommensurate supercell reflections is described. The code is completely general, being applicable to any crystal system, and can refine all three unit cell edges and angles and, in the presence of an incommensurate supercell, can refine the components of the modulation vector along all three reciprocal axes. Estimated standard deviations on all the refined parameters are calculated analytically.

The design and construction of Geiger-Müller counters which will respond reliably to Mo K x-rays is described. The impulses are amplified and recorded mechanically with the aid of a thyratron circuit. The amplifying and counting circuit, and the counting mechanism, are also described. The time of recovery of the counters has been determined by the use of an oscillograph and found to be less than 0.001 sec. when the proper values are used for the resistance and capacitance of the counter circuit. It is shown that for counting rates up to 600 per minute there is less than a 1 percent correction due to the fact that the impulses are random in nature. Several fundamental tests are described, which have been applied to the counter and the circuit. These tests have shown the counter and the circuit to be a reliable method of measuring x-ray intensities. Graphs are shown of the diffraction patterns of NaCl and KC1 taken by means of the counters. These graphs duplicate the well-known diffraction patterns of these materials, thus giving additional evidence of the reliability of the counters.

A method for quantitative characterization of a phase's depth distribution is discussed in detail. Both model-independent and model-dependent nonlinear least squares technique methods were developed; in addition, an inverse Laplace transformation method is presented to solve the problem directly in mathematics. The methods can also be used for samples with preferred orientation. Furthermore, the technique is expanded to the technique of computed depth profiling of XRD patterns; then the depth profiles of other structural information that is based on the peak intensity, peak position, and line profile can be determined. A feasibility test was also performed.

A program has been written for rapid lattice parameter refinement which is designed to be applied to components in a mixture. This FORTRAN program employs a linear least-squares technique and is applicable to crystal systems with symmetry orthorhombic or higher. In addition to lattice parameters, a 2θ-zero can also be refined. Either approximate lattice parameters or a minimal set of indexed lines can be used as input. An example is given of its application to a AuMn two phase system.

Powder samples for diffraction studies of selected materials have been prepared in this laboratory during the past 15 years using a commercial, slow-speed, diamond saw. The materials powdered include a wide range of ferrous and transition metal alloys as well as geological substances. Before sectioning begins, fresh oil is poured into the oil tray of the saw and the diamond, rim-impregnated, copper blade thoroughly cleaned. A typical blade is 10 cm in diameter and 3 mm thick. Powder produced as the blade cuts through the sample collects in and settles to the bottom of the oil tray. The oil, which bathes the sample surface during cutting and surrounds the powder debris after discharge into the tray, serves to prevent oxidation of most materials.