Samples of airborne particulate were collected at the “El Ingenio” site in Castellón (Spain) using a cascade impactor sampler. Quantitative analysis of present phases in the aerosol was performed using the full-pattern fitting Rietveld method. Quantitative information was obtained from refined individual scale factors and unit-cell volumes, obtained with a Rietveld refinement program. Quartz, calcite, and gypsum were encountered as major phases, and their size distribution and concentration in the atmosphere were calculated.

A special computer storage method for chemical structures is illustrated in this article. With an improved method of two-dimensional connection table and topology, we can fit almost all chemical structures and display them very conveniently. We have used this method in the PDF (X-Ray Powder Diffraction File) database, which contains many special structures.

Key words: database, computer application, chemical structure

A general expression for the method of QXRPD without standards is given in this paper to solve the problem of phase analysis on samples containing a non-crystalline component. Its application to some specific cases is discussed. The experiments have proved successful in the analysis of cement and sand-lime samples. The technique may also be applicable for the analysis of fly-ash, glass, ceramics, and metals. It is especially convenient in the study of kinetics and mechanism of reactions when the chemical composition of all samples does not change, because it is not necessary to know the mass absorption coefficient of samples. In the mathematical treatment of non-linear equations given in this paper, a method called linearized iteration procedure is first presented by the author.

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.

Substituting cations in materials with the formula Pb2B′B″O6 is more or less ordered on the B sites. High-quality single crystals of Pb2ScTaO6 (PST) and Pb(Sc0.5Nb0.5)O3 (PSN) were prepared from two thermal cycles. A stoichiometric mixture of the constituent oxides was prefired at up to 1000 °C, and then crystals were grown from a PbO–B2O3–PbF2 flux mixture, starting at a temperature of 1100 °C for PSN and 1200 °C for PST. At room temperature, X-ray examination showed that PSN had a perovskite structure with a cubic unit-cell and a refined parameter a = 4.080(1 ) Å, space group Pm3m and Z = 1, whereas PST formed a well-ordered superlattice with a = 8.136(1) Å, Z = 4 and space group Fm3m. In each case a fully indexed powder pattern is presented. The degree of order is estimated to be close to 80% for PST and less than 10% for PSN.

X-ray powder diffraction data for the compound Di-(1-phenylisopropyl)formamide, C19H23NO are reported. The crystals are monoclinic and the space group P21/c, with a = 10.764(2), b = 14.893(2), c = 10.862(2) Å, β= 108.49(1)°, Z = 4, Dx= 1.132, Dm= 1.120(2) gm/cm3.

Fifteen reference patterns of boride, silicide, selenide, telluride and oxide ceramics are reported. Included in the 15 reference patterns are data for three oxide phases which are related to high critical temperature (Tc) superconducting materials: BaCuO2, BaCuSm2O5 and BaCuYb2O5. Four other patterns are included which represent phases previously not contained in the PDF. The remaining six are major corrections of data already included in the file. Reference data for phases Ba2CuY3O6.8 and Ba2Y3CuO6 appeared in the special July superconductor issue of the Advanced Ceramic Materials, 1987. The general methods of producing these X-ray powder diffraction reference patterns are described in this journal, Vol. 1(1), 40 (1986).

Samples were mixed with one or two internal standards: silicon (SRM640a), silver, tungsten, or fluorophlogopite (SRM675). Expected 2θ values for these internal standards are specified in the methods described (ibid.). Data were measured with a computer controlled diffractometer. The POWDER-PATTERN system of computer programs was used to locate peak positions, to calibrate the patterns, and to perform variable indexing and least-squares cell refinement. A check on the overall internal consistency of the data was also provided by a computer program.

The influence of grinding procedures on the intensity and full-width-half-maximum for the 101 line of the X-ray powder diffraction pattern for α-quartz has been investigated using samples of controlled grain size. Data collected on powders obtained by four dry grinding methods show substantial variations (up to 35%) in the quartz diffraction intensities. These variations are evident in the <5 μm size fractions and are attributed to the creation of different thickness of amorphous silica layers on quartz grains by grinding. This result suggests that optimum grinding conditions should be defined for quantitative X-ray diffraction analysis.

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.

CeO2 transforms to an orthorhombic PbCl2-type structure at a pressure of about 31 GPa. The phase transition is accompanied by a 9.8% volume contraction. The bulk modulus of the low-pressure fluorite-type structure is 236(4) GPa. Comparisons are made with the high-pressure behaviour of UO2 and ThO2.

High-quality powder X-ray diffraction data for a well-characterised natural sample of natrolite (Na2Al2Si3O10.2H2O, space group Fdd2, Z = 8) are presented. Refined cell parameters were a = 18.2984±0.0007 Å, b = 18.6502±0.0008 Å, and c = 6.5589±0.0003 Å. The sample was characterised using thermogravimetric techniques (to determine water content), EPMA and ICP-MS (to determine composition). Available data suggest that the crystal matches the expected stoichiometry of natrolite. Our powder data show close similarity with the proposed structure of natrolite using the Rietveld method, giving R values of 8.54%, and suggest that preferred orientation is not present in the sample.

Five structurally related compounds, TlMgAsO4, TlMgPO4, TlZnAsO4, TlZnPO4, TlZnVO4, have been synthesized by solid-state reaction. Single crystals have been grown by various methods. Space group and unit-cell parameters were determined. Powder diffraction data for each phase are reported.