The procedure of whole-powder-pattern fitting without reference to a structural model has been applied to the determination of direction-dependent crystallite size and strain. The fitting function used is defined as the sum of (1) background intensity and (2) contributions from individual reflections given as the convolution of the observed instrumental function with the true data function in analytical form. Crystallite size and strain parameters are adjustable, together with unit-cell parameters and the integrated intensities of all reflections, during the whole-powder-pattern fitting. The procedure requires neither structural parameters nor intensity correction for preferred orientation in calculating profile intensity. The two models are incorporated for line broadening, one for isotropic size and strain effects and the other for the anisotropic size effect of cylindrical shape. The procedure has been tested for these two models using the observed data of 4 mole % Y2O3-doped tetragonal ZrO2 and hydroxyapatite, Ca5(PO4)3OH, respectively, and been shown to be effective for determining crystallite size and strain from the powder pattern with a relatively high peak density.

A new Peltier-cooled solid-state Si(Li) detector has been compared to a traditional scintillation detector/diffracted-beam graphite monochromator system in conventional X-ray powder diffraction applications. Parameters studied included absolute count rates, detector linearity, peak-to-background ratios, detection limits, fluorescent radiation elimination, and peak profile shapes. Comparisons were performed on a Siemens D-500 θ-2θ diffractometer using constant sample and nondetector instrumental parameters. Advantages of the Si(Li) detector include a significantly increased count rate (3.4 - 3.8 times), primarily due to the elimination of the graphite monochromator, slightly lower background count rates, and the ability to change the analysis energy quickly. The higher count rate and slightly lower background count rate of the Si(Li) detector allow collection of data more rapidly than possible with a scintillation detector/diffracted-beam monochromator system and yield improved peak-to-background ratios and detection limits. Significant disadvantages of the Si(Li) detector include pronounced deviation from linearity at low count rates, making accurate measurement of even moderate countrate peaks difficult, and detector shutdown due to 100% deadtime between 4 and 5 × 10 4 counts/s (cps). The Si(Li) detector and the scintillation detector/diffracted-beam monochromator system are comparable in terms of fluorescence radiation elimination, resolution, and peak shape, although it appears tfiat die diffracted-beam monochromator measurably reduces the low-angle portion of the half width of all reflections.

Fourier self-deconvolution has been successfully applied as a means of obtaining semi-quantitative information by resolving the overlapping peaks in X-ray powder diffractograms collected from mixtures of kaolinite and ripidolite. A series of diffractograms were collected from known mixtures of the two minerals. The diffractograms were then processed using Fourier self-deconvolution over a selected range between 23 and 27° 2θ (encompassing the overlapping peaks of kaolinite (002) and ripidolite (004) at 24.85 and 25.13° 2θ, respectively). Once deconvoluted, areas under individual peaks of kaolinite and ripidolite were calculated using curve fitting. The calculated percentage of kaolinite in the mixtures was then plotted versus the true weight percent of kaolinite. The same procedure was conducted on the original diffractograms using only curve fitting without first deconvoluting. A comparison of results shows that, provided the number of peaks are known, both methods give nearly equal results. However, Fourier self-deconvolution, by increasing the resolution, greatly improves the ability to detect overlapping peaks.

Room temperature crystalline structures of La2-xSrxCuO4 samples with uncommonly high hole concentrations (p) up to p=0.4, annealed under 1 and 100 bars of oxygen pressure have been analyzed by X-ray diffraction. Results show that the x=0 sample with p=0.09 and superconducting below 20K is orthorhombic at room temperature. The orthorhombic distortion at 300K decreases with increasing x and becomes tetragonal when x reaches 0.08. This orthorhombic-to-tetragonal phase transformation is consistent with previous work. Samples with x≥0.28 and p≥0.31 remain tetragonal but are nonsuperconducting down to 5K. Lattice dimension anomalies have also been observed and are correlated with the sudden appearance of oxygen vacancies, as seen by the hole concentration measurements. Initially, the value of the lattice dimension a decreases and c increases monotonically with increasing x. A sudden increase in a and decrease in c begins when x reaches 0.28 for samples prepared under 1 bar of oxygen indicating a sudden loss of oxygen from the structure. This sudden reversal in lattice dimensions a and c is not present in samples annealed under 100 bars of oxygen pressure suggesting essentially no oxygen vacancies. The increase in c with x of the La2-xSrxCuO4 samples with no oxygen vacancies can be attributed mainly to the result of substituting smaller La+3 ions by larger Sr+2 ions. A study of the variation of c with the hole concentration reveals that the c lattice dimension drops sharply with no change in the hole concentration when oxygen is continuously removed from the lattice caused by an increase of the Sr content in La2-xSrxCuO4.

The Powder Diffraction File (PDF) X-ray diffraction pattern for SnO2 (cassiterite, syn), determined in the early 1950's at the National Bureau of Standards, was evaluated using the NBS*AIDS83 editorial review program and a calculated powder pattern. Systematic errors in d-spacings and relative intensities were attributed to the lack of an iterative least-squares refinement of unit cell parameters, to inadequate precision in reporting d-spacings, to poor sensitivity to high angle reflections, and to detector dead time. A new SnO2 pattern was prepared and used to illustrate criteria for evaluation of powder patterns. An R-Factor for quantifying agreement between observed and calculated relative intensities was utilized. The systematic errors in the earlier pattern occurred at higher angles and did not hinder its usefulness for identification purposes.

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.

Three members of the family [CuC15H11N3)X2]·nH2O [X−=NCO (n=1), NCSe and N3 (n=ø)], C15H11N3=2,2′:6′,2″ – terpyridine (terpy), have been prepared by reaction in solution. Crystal data determined widi the aid of single crystal methods, powder diffraction data, and densities determined by flotation methods are presented.

Three isotopic orthovanadates MTh2 (VO4)3 with M = K, Rb, Cs have been syndiesized by solid state reaction. Single crystals of K Th2 (VO4)3 and Rb Th2 (VO4)3 were obtained. These compounds are isotypic with the corresponding orthophosphates: monoclinic, space group C2/c, Z = 4. Unit-cell parameters for die diree compounds were determined. Powder diffraction data for each phase are reported.

Indexed powder diffraction patterns and related crystallographic data are reported for tetracycline-urea tetrahydrate and tetracycline hexahydrate, neither of which is represented in the X-ray Powder Diffraction File. Objective evaluation of the data indicates high precision of d-spacings and unit-cell parameters, intensities that are acceptably reproducible, sensitivity for low intensity reflections, good resolution of closely spaced reflections, and close correspondence with calculated patterns.

New X-ray powder data and a refined cell for mellite are presented and evaluated in comparison with the current PDF 28-2001.

The synthesis, thermal behavior, crystallographic and X-ray powder diffraction data, and infrared spectral data for Ca8ZnSi4O16Cl2 have been determined. This compound is cubic with isolated silicate tetrahedra.