An interactive computer program to display, process and analyze raw powder X-ray diffraction data is described. The program extensively employs graphic means of input and output with the help of “pop-up” windows and menus. In addition to those tasks that are common to most primary raw data analyzing programs, it performs many functions which are generally assigned to separate secondary programs. These functions include on-screen correction of d-spacing with reference to a standard compound, calculation of peak width and crystallite size, subtraction of patterns for differential X-ray diffraction and unrestricted overlay of patterns. The advantages of an integrated single program to process X-ray diffraction data in mineral research are illustrated and discussed.

The hydration of ordinary Portland cements (OPC) was investigated with X-ray powder diffraction (XRPD) technique, mainly using synchrotron radiation. In situ experiments were performed during the first hours of hydration to study the evolution of the crystalline phases in the system. The hydration was carried out with pure water and in the presence of additives such as superplasticizers and setting accelerating agents. As soon as water is added to the cement, ettringite crystallizes. Its evolution appears to be very complex, and lattice parameters change as a function of setting time, indicating a possible chemical evolution of ettringite with time and as a function of pH. CSH (Ca-Si-hydrate) forms after a few hours from the beginning of hydration. CSH can be indirectly quantified and its evolution studied.

Quantification of potentially toxic single mineral phases in natural dusts of heterogeneous composition is critical for health hazard assessment. For example, crystalline silica, a human carcinogen, can be present as respirable particles in volcanic ash such as quartz, cristobalite, or tridymite. A method to rapidly identify the proportions of crystalline silica within mixed dust samples, such as volcanic ash, is therefore required for hazard managers to assess the potential risk of crystalline silica exposure to local populations. Here we present a rapid method for quantifying the proportions of single phases in the mineral assemblage of mixed dusts using X-ray diffraction (XRD) with a fixed curved position-sensitive detector. The method is a modified version of the whole-pattern peak-stripping (PS) method (devised by Cressey and Schofield [Powder Diffr.11, 35–39 (1996)]) using an internal attenuation standard (IAS) but, unlike the PS method, it requires no knowledge of other phases present in the sample. Ten synthetic sample mixtures were prepared from known combinations of four pure phases (cristobalite, hematite, labradorite, and obsidian), chosen to represent problematic constituents of volcanic ash, and analyzed by XRD. Results of the IAS method were directly compared with those of the PS method. The proportions of cristobalite estimated using the methods were comparable and accurate to within 3 wt %. The new IAS method involved less sample preparation and processing and, therefore, was faster than the original PS method. It therefore offers a highly accurate rapid technique for determination of the proportions of individual phases in mixed dusts.

The modal analysis of samples belonging to the zeolite-rich pyroclastic formation named “Neapolitan yellow tuff” (Central and Southern Italy) has been determined by full-profile refinement of X-ray powder diffraction (XRPD) data using a combined Rietveld–RIR method. The quantitative analysis and especially the zeolite content is a profitable source for geo-petrographic and genetic considerations and as well an essential source to assess the physical and chemical properties of the bulk material for a feasible use in industrial applications. Albeit a wealth of methods are used for the quantitative determination of zeolite content in pyroclastites they all fail for lack of accuracy as far as concerns the absolute standard deviation of the quantitative data. The outstanding outcomes achievable by using the Rietveld method make it as the most promising technique to fulfill this lack. The glass content in each sample is calculated by a combined Rietveld–RIR method in which a known amount of an internal standard is added to the mixture to rescale the Rietveld refined weight fractions into absolute values. Then, it is reasonable to designate this method as an external method according to the definition given by Hill and Howard (1987). Its counterpart is the internal method developed by Riello etal. (1995a,b). Other techniques such as the addition method and the background scattering volume calculation are developed to accomplish a further determination of the glass content. The results are compared to the values obtained from the Rietveld–RIR analysis. These experimental methods yield an over-estimation of the amorphous phase because the incoherent scattering contribution (air, absorption, sample holder, Compton scattering) is accounted for as the amorphous fraction itself. The glass content of each sample acquired from the Rietveld–RIR refinement on the “raw data” is compared to that accomplished from the refinement of incoherent scattering subtracted data. In addition, some largely used XRPD quantitative techniques such as the external standard and RIR (reference intensity ratio) and the influence of the sample loading method are accounted for in an internally consistent comparison among different procedures of analysis.

Rietveld refinement using neutron, laboratory X-ray, and synchrotron powder diffraction data of NIST SRM clinker 8488 was performed. Quantitative phase analysis (QPA) results were compared between data, and with other studies. QPA results for the main phases in the clinker were found to be in agreement between the different data used here, and in and other studies, although the QPA of the tricalcium silicate polymorphs was shown to be inconsistent. The QPA results for the tricalcium aluminate phase varied between data types, and the neutron data were unable to distinguish this phase.

Weld residual stress (RS) measurements are often undertaken on test-pieces which have been cut out from large components, yet it remains unclear to what extent the RSs in test-pieces are representative of those present in the original component. Similarly weld mechanical performance tests are frequently undertaken on cross-weld test-pieces without a proper understanding of the level or influence of retained RS. We present a systematic study of the relaxation of longitudinal RS in thin-plate butt welds produced using different materials and welding methods (FSW, laser-MIG, and pulsed-MIG). In each case the RSs were measured repeatedly in the same location as the welds were progressively and symmetrically cut down. Although cutting inevitably leads to stress redistribution, significant relaxation of the longitudinal RS was only observed when the weld length or width was reduced to below a certain value. This critical value appears to correlate with the lateral width of the tensile zone local to the weld-line and may be considered to be the characteristic length as defined in St. Venant’s principle. Further, it was found that the level of stress relaxation as a function of weld length for all the welds studied could be collapsed onto a single empirical curve using a simple approach based on the characteristic length scales of the weld. Given the range of materials and welding methods used, this relation appears to be of general use for thin-plate welds although further work is required to test the limits of its applicability.

Gamma-phase lithium aluminate (LiAlO2) is a ceramic powder used in molten carbonate fuel cells (MCFCs) and in other nuclear and ceramic applications. Upon exposure to water vapor and carbon dioxide at 25 °C, we have observed that gamma-LiAlO2 converts to lithium aluminum carbonate hydroxide hydrate, Li2Al4(CO3)(OH)12·3H2O(LACHH) and Li2CO3. The conversion was observed by X-ray diffraction (XRD) and carbonate analysis. An equation for the conversion is given, and the morphology is determined by scanning electron microscopy. A high-temperature XRD study and thermogravimetric/differential thermal analysis (TGA/DTA) showed that LACHH decomposes at 250 °C. The decomposition products of LACHH and Li2CO3 react to form first alpha-LiAlO2 and then gamma-LiAlO2 at temperatures of 650 and 1000 °C, respectively.

An additional statistical calibration for the Bruker D8 Discover microdiffractometer is necessary to obtain accurate reproducible 2θ data for cell-refinement work. This new approach uses a graphical mapping method of the 2θ error versus the location of a selected diffraction peak on the detector surface to describe the separate roles of different calibration procedures (rebiasing, flood field, and spatial corrections) and parameters (sample-to-detector distance, x-y center coordinate) in minimizing the error. Optimized parameters are used to obtain the lowest achievable Δ2θ with this setup. Intensity error relative to the position of the diffracted line on the detector was found to be consistent at up to 20% and could not be reduced using any of the investigated techniques and parameters.

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

Doubly curved crystal (DCC) X-ray optics provide an enabling technology for new portable, remote, and in situ applications of monochromatic X-rays for composition and structure analysis of amorphous, polycrystalline, and crystalline solids. Femtogram sensitivity for surface contamination, parts-per-billion (ppb) impurity levels for solids, and composition, structure and uniformity of thin films with compact, low power (20–50 W) source optic combinations are possible.

The phases developed upon annealing of ZnSe, CdSe, and CdS semiconductors in air are investigated applying X-ray qualitative and quantitative phase analysis. The compositions of the thermally grown oxides over the 373–773 K temperature range are found to be ZnO and ZnSeO3 for ZnSe, CdSeO3 for CdSe and CdSO4 and Cd3O2SO4 for CdS. The percentage phase abundance of each phase is determined at each temperature applying a standardless method. At all temperatures, the oxides are predominantly ZnO with about 10% ZnSeO3 at 773 K in case of ZnSe and CdSO4 with about 9% Cd3O2SO4 at 773 K in case of CdS. The rate of oxidation with temperature is found to be nonlinear for the three chalcogenides. CdS is found to be more resistible for oxidation than CdSe and ZnSe.

A new structural model is proposed for cubic nitroprussides and the crystal structure for the complex salts of Fe(2+), Co(2+), and Ni(2+) refined in that model. In cubic nitroprussides the building unit, [Fe(CN)5NO]2−, and the assembling metal (M=Fe2+,Co2+,Ni2+), have ¾ occupancy with three formula units per cell (Z=3). This leads to certain structural disorder and to different local environments for the outer metal. The crystallographic results are supported by the Mössbauer and infrared data. The XRD powder patterns, index in a cubic cell (Fm3m space group), show a sinuous background because of diffuse scattering from positional disorder of the metal centers. Because of this, the crystal structures were refined allowing the metal centers to move from the (0,0,0) and (0,0,1/2) positions (away from positional symmetry restrictions). The refinement under these conditions leads to excellent agreement factors (Rwp, Rp, S), good pattern background fitting, and produced a refined structural model consistent with the crystal chemistry of nitroprussides. The studied materials are obtained as hydrates. On heating, the crystal water evolves, and below 100°C an anhydrous phase is obtained, preserving the framework of the original hydrates. The loss of the crystal water leads to cell contraction that represents around 2% of cell volume reduction. On cooling down from room temperature to 77 and 12 K, a slight expansion for the -M-N≡C-Fe-C≡N-M- chain length is observed, suggesting that at low temperature and reduction in the metals charge delocalization on the CN bridges takes place. For M=Fe and Co the crystal structure was also refined for the anhydrous phase at 12, 77, and 300 K.

The following new or updated patterns are submitted by the JCPDS Research Associateship at the National Bureau of Standards. The patterns are a continuation of the series of standard X-ray diffraction powder patterns published previously in the NBS Circular 539, the NBS Monograph 25, and in this journal. The methods of producing these reference patterns are described in this journal, Vol. 1, No. 1, p. 40 (1986).

The data for each phase apply to the specific sample described. A sample was mixed with one or two internal standards: silicon (SRM640a), silver, tungsten, or fluorophlogopite (SRM675). Expected 2-theta values for these standards are specified in the methods described (ibid.). Data, from which the reported 2-theta values were determined, were measured with a computer controlled diffractometer. Computer programs were used to locate peak positions and calibrate the patterns as well as 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 crystal structure of low temperature NaNiO2 has been refined by Rietveld methods using powder X-ray diffraction and neutron scattering data. The starting model was based on parameters that had been obtained earlier by X-ray film methods. At room temperature NaNiO2 is monoclinic, C2/m, a=0.53192(2), b=0.28451(1), c=0.55826(4) nm, β=110.449(2)°. NaNiO2 has a layered structure. The Ni–O layer is formed by edge sharing of Jahn–Teller elonganted NiO6 octahedra with Ni–O distances of 0.1911(2) nm and 0.2144(4) nm. The Na ions between these layers also exhibit a distorted octahedral coordination with Na–O distances of 0.2328(2) nm and 0.2369(4) nm. The final R values were Rwp=0.069, RI=0.059, Rexp=0.059 for the neutron and Rwp=0.032, RI=0.034, Rexp=0.017 for the X-ray data.

With the explosive growth in the number of highly automated powder diffraction systems, many types of analyses which were previously considered a specialty analysis are now performed on a routine basis. Algorithms have been developed for measuring peak profiles from which crystallite sizes, residual microstrain, and X-ray crystal structure (Rietveld techniques for example) can be determined. However, these techniques require an instrumental peak profile calibration standard to correct the experimental data for instrumental broadening due to the system optics.

Significant problems are encountered when laboratories try to cross-correlate or reproduce published data due to the lack of a common reference material for instrumental calibration. This is particularly distressing in microstrain and crystallite size calculations which can be dramatically affected by a poor choice of standard materials. Microstrain and crystallite size measurement are becoming increasingly important for the characterization of advanced materials and catalysts.

The structure of TeO3, first published by Dumora and Hagenmuller (1968), was redetermined from new X-ray data collected with a powder diffractometer using space group R3̄c with a = 4.901(2), c = 13.030(4) Å, V = 271.05(8) Å3 and Z = 6. Intensity data were obtained with CuKα, radiation (λ = 1.540598 Å). Structure refinement was performed with 49 reflections and led to R = 0.058. The material is isostructural with FeF3. Powder data are given.

The relative intensities ratios for the determination of the relative amounts of alpha and beta phases in silicon nitride and the relative amounts of delta yttrium disilicate (Y2Si2O7) and nitrogen apatite [Y5(SiO4)3N] are reported. These constants were determined using an iterative method applicable when the pure phases are not easily prepared. In addition, a calibration curve was obtained for the quantitative measurement of free silicon in silicon nitride over the range 0 to 0.3% by weight of Si.

Icosahedral boron phosphide (B12P2) was directly synthesized from elemental powders by a high-temperature reaction under an argon pressure. Powder diffraction data were collected for two B12P2 samples, and diffraction patterns were compared with calculated patterns of phosphorus deficient crystals: B12+xP2−x for 0<;x<0.2. The as-synthesized B12P2 appears to be close to its ideal stoichiometry based on the consistency between the observed and the calculated values of the relative intensity for all diffraction planes below 90° 2θ.

A nonlinear optical material, o–chlorobenzol–benzoyl thiourea (C14H11ClN2OS), has been characterized by X-ray powder diffraction. Experimental values of 2θ corrected for systematic errors, relative peak intensities, values of d, and the Miller indices of 78 observed reflection with 2θ up to 72° are reported. The powder diffraction data have been evaluated, and the figures-of-merit are reported. The unit cell parameters least-squares refined from 28 nonoverlapping peaks of the monoclinic compound with a P2 space group are a=13.2797(4) Å, b=12.4058(8) Å, c=8.1561(2) Å, β=95.398(1)°, V=1337.7(4) Å3, Z=4, Dx=1.444 g/cm3. © 1997 International Centre for Diffraction Data.

Crystal structure of the skutterudite-related phase has been refined by the Rietveld method from X-ray powder diffraction data. Refined crystallographic data for CoSn1.5Te1.5 are a=12.9063(2) Å, c=15.7837(3) Å, V=2276.89(4) Å3, space group R3 (No. 148), Z=24, and Dx=7.50 g/cm3. The crystal structure of the title compound can be viewed as a modification of the skutterudite structure (CoAs3)—it is isostructural with CoGe1.5Te1.5 and IrSn1.5Te1.5. In the structure of CoSn1.5Te1.5, the Sn and Te atoms exhibit long-range ordering, which results in lowering of the original cubic symmetry of the skutterudite structure to the trigonal one.