The development of preferred orientation, by powder compaction was studied in several single phase, two-phase and three-phase powders. It was found that texture formation depends strongly on the properties of the powder particles and the preparation technique. In powder mixtures strong interaction effects were observed which either enhanced or reduced the degree of the preferred orientation. The required degree of series expansion of the texture function ranged from zero up to about fourteen.

A wavelength dispersive spectrometer which consists of a flat crystal analyser and a position sensitive proportional counter has been developed for X-ray fluorescence analysis using synchrotron radiation. The advantages of this spectrometer are high energy resolution, multielemental nature, and high efficiency, and these match well "with the high brightness synchrotron X-ray source. The minimum detection limits are of the order of ppm or pg. An application to elemental mapping has also been demonstrated. The present system is useful for practical analysis of small samples or small regions.

The semi-quantitative analysis, which is called ‘Standardless Analysis’, plays a major role in X-ray fluorescent analysis, especially in the field of research and development. The main feature of the semi-quantitative analysis is the fact that the composition of a sample can be obtained directly from a qualitative scan without any prior knowledge of the sample.

Polycrystalline and powder diffraction is the most commonly practised method of x-ray analysis. During the last decade the construction of dedicated synchrotron radiation sources has resulted in the renaissance of these x-ray analysis methods; ab initio structure analysis and refinement, quantitative analysis of the structure, composition and stress in thin films and on surfaces, have all been improved. New techniques providing extremely high resolution, using anomalous dispersion, diffraction and scattering at grazing incidence to control x-ray penetration depth, have been developed. This brief review of work with W. Parrish at Stanford Synchrotron Radiation Laboratory and R. J. Cernik at the Daresbury Synchrotron Radiation Source is extended to indicate how third generation sources might be exploited in materials science.

During the course of the past ten years the International Centre for Diffraction Data has sponsored a number of “Round Robin” tests to evaluate the quality of experimental X-ray diffraction data [1-5]. The latest of this series, called the Instrument Parameter Round Robin, was designed to evaluate, among other things, relative angularly-dependent sensitivity differences between diffractometers. Previous experiments have indicated that even perfectly aligned diffractometers of the same generic type, do not necessarily give the same set of relative intensities. One objective of the round robin was to quantify the magnitude of the experimental differences between data sets, and to demonstrate a means for external calibration of diffractometers, so that digitized diffraction intensity data obtained from different instruments could be directly compared.

The use of a field portable XRF analyzer incorporating a semiconductor, mercuric iodide, energy dispersive spectrometer is described with emphasis on the benefits of high resolution x-ray detection for rapid screening of hazardous metallic wastes. Results are presented of “in-situ” and “prepared sample” soil measurement for different sites to show the potential of Fundamental Parameter analysis to obtain acceptable quality data with minimum calibration effort, obviating the need for site-specific standards.

Improvements in sample preparation methods have resulted in increased accuracy in x-ray powder diffraction intensity measurements. This improvement has focused scrutiny on the instrument as a potential source of error. NIST Standard Reference Material, SRM, 1976 consists of a sintered α alumina, corundum, plate certified with respect to 12 relative intensity values from 25 to 145 degrees 2θ. Its function is to allow for standardization of powder diffraction intensity as a function of 2θ angle (instrument sensitivity). An increase in the accuracy of interlaboratory comparisons of diffraction intensity and related determinations will result. Utilization of the SRM requires the user to collect intensity data from the test instrument in a manner which conforms to that used in the certification. Graphical interpretation of the ratio of these data to those on the certificate will allow for appropriate judgment as to the condition of the test instrument. Discontinuities in the data indicate a malfunctioning or misaligned instrument. Systematic bias, introduced by design characteristics of the test instrument, manifests itself in terms of a pattern in the data other than a horizontal straight line with value of one. This bias may be removed with the calculation and application of a correction curve.

A new experimental calculation method for polydisperse (i.e. heterogeneous) multicomponent material analysis has been developed using the dependence of element fluorescence intensity on the particle size and its distribution in the specimen. It is shown that correction of the influence of matrix particle size is possible using this experimental calculation method. For its application, the information on particle size distribution for each of the components is sufficient. Sample preparation includes only the pelleting of specimens under standard conditions. The efficiency of the method proposed is demonstrated by the analysis of the multicomponent mixtures of welding materials.

An x-ray microfluorescence (XRMF) spectrometer has been designed and fabricated at NIST for multi-point compositional analysis of small samples with x-ray beam sizes on the order of 50 micrometers or greater. This system was developed as part of an industrial cooperative research agreement with Kevex Instruments, Inc., San Carlos, CA., and consists of commercially available components incorporated in an aluminum vacuum chamber (see Figs. 1 and 2).

The need for reliable standards for the characterization of x-ray powder diffraction (XRD) instruments has been well documented. As a result of the round robin study, of various candidate standard materials, described by Fawcett et al., the National Institute of Science and Technology has made the SRM-660, lanthanum hexaboride, XRD peak width standard available. It has been normal practice to use powder sample standards for XRD powder diffraction studies. Powder standards have been justified on the principle that standards should be as much as possible like the unknowns to be analyzed; however, standards must be quite different from the unknowns because their peak profiles must be as narrow as possible for deconvolution from sample peak profiles. It would seem most advantageous to use standards of the highest degree of crystallinity so that they would be useful over the maximum number of applications. Single crystals, with their extremely high crystallinity, offer that advantage.

Refraction effects cause the effective 2d spacing of multilayers to vary so that the simple Bragg equation is not applicable when such devices are used for soft X-ray spectroscopy. This paper describes how the refraction term can be determined experimentally. These results compare well with dispersion and absorption terms calculated from atomic scattering factors.

Silicon powder, available as a Standard Reference Material, fulfills most of the requirements for a two theta standard. However, It has no diffraction lines at the low 2θ values characteristic of some species. Standard synthetic mica is available but expensive.

Experiments with a commercially available high silica zeolite have shown that it is a valuable secondary standard. It is non-toxic, stable, inexpensive and possesses a large (24 Å) unit cell. Peaks show clearly from 14 Å (6°2θ for Cu Kα).

An example is given of the use of this secondary standard in determining lattice parameters.

Trace analysis of quartz at the <0.1 wt% level can be routinely accomplished by x-ray diffraction using rotating pressed-powder briquettes and a peak deconvolution strategy due to Wiedemann, et al. (1937a, b) which permits reproducible determination of background and enhances peak resolution without changing the integrated intensity.

Four calibration methods were tested: (1) calibration with perlites microscopically analyzed by Hamilton and Peletls (1988), (2) with artificial mixtures of quartz and glass, (3) with chemical analysis and massbalance calculation of quartz in glass mixtures, and (4) with a new method of additions for XRD.

Methods (2) and (4) gave the best results. Method (2) has a precision of 16.9 pet at the 0.1 wt% level and a LLD of 0.05 wt% at 3σ. Method (4) is particularly attractive because large spikes can be used which minimize homogenization errors and permit preparation of standards which have properties very similar to run-of-the-mill samples; the problem of non-zero intercepts is avoided.

A method of semiconductor detector calibration by variation of the incidence angle of the x-radiation is discussed.

A monochromatic and linear polarized X-ray beam obtained by a Bragg reflection of a characteristic tube line under 90° on single crystals can be used as a EDXRF excitation source in a triaxial beam geometry in order to profit by the polarization effects reducing the scattering background in the fluorescence spectrum, A systematic selection procedure for 55 single crystals suitable for Bragg reflection was established. The selection procedure takes the following conditions and criteria into account. First of all the existence of appropriate lattice planes hkl fulfilling the Bragg reflection condition and having low Miller indices as well as a Bragg angle close to 45° ensures a high degree of polarization. Furthermore the integrated reflectivity Ri for these lattice planes should be as high as possible. For the validity of the formula for Ri of an ideal mosaic crystal, the effects of primary and secondary extinction as well as of true absorption have to be considered. The critical limits of these parameters are calculated. The results of this systematic crystal selection procedure for the characteristic Kα lines of Cr, Cu, Mo and Ag tubes are presented.

Recently some of the above authors determined the structure of an unsolved organic compound employing X-rays from a Synchrotron, an Imaging Plate, and a large radius camera. It would be more desirable if the high quality powder diffaction data could be obtained by a diffractometer or a camera of laboratory use. Therefore a multimode X-ray powder diffractometer which can be used for various experimental geometries such as Bragg-Brentano mode, Guinier mode and parallel beam mode was constructed in order to find the highest resolution geometry. In this paper wc present the results of the measurements employing these three modes.

We propose a method, by absorption [1,2,3,4], of determination of the X-ray spectrum emitted by a flash X-ray radiography generator. This approach leads to an ill posed inverse problem very sensitive to the measures precision.

We improve the robustness of the method by introduction of a smoothness constraint on the X-ray spectrum to reconstruct. We also propose an automatic choice of the weight between the measurement and the constraint by using a cross-validation technique.

We present an application on an unusual flash X-ray radiography generator - i.e. 75 ns of duration pulse, 6.5 MeV of maximum energy, 350 Rad for dose - for which an instrument of direct measure has not yet been found.

The Bragg-Brentano focussing method (2θ/θ scan) is widely used in X-ray powder diffractometers. We have recently manufactured a diffractometer (2θ/α scan) whose incidence and reflection sides are asymmetrical. This report describes the optical system, including evaluation and application. The present method enables the following benefits to be obtained by simply changing the sample-to-receiving slit distance b without changing the X-ray source-to-sample distance a: (1) enhanced angular resolution, (2) increased diffracted X-ray intensity, and (3) variable asymmetrical angle. The experimental results show that the focussing condition of this optical system was satisfied. It also shows that the intensity of diffracted X-rays could be increased by approximately 1.4 times at b = 100 mm when the intensity at a = 185 mm and b = 185 mm was assumed to be 1. Furthermore, it was verified that FWHM can be reduced by making sample to receiving slit distance greater.

A two-crystal spectrometer for chemical state analysis by high-resolution x-ray fluorescence spectrometry employs hall-screw and slide mechanisms rather than gears to obtain a 2θ scanning range of 40° -147°; a Δ2θ scanning step of 10−4 deg under vacuus; a 2θ resolution of 10−4 deg in determination of an intercrystal angle with encoder-based measurement; and servomechanical control of position. The spectrometer, although simple in structure, is a powerful instrument for chemical state analysis, as demonstrated by its high resolution, precision, and stability; as demonstrated in the determination of the Kα1 lines of first transition metals with Si(220) as analyzer crystal, and in its application to a systematic study of the chemical effects on Ni Kα1 and Kα2.

In general Latin America countries function differently in respect to the rest of the world because of their geographic allocations, economic and social situations. The areas of science and technologies are not excluded from this general rule. Thus, the following question arises : How has the area of analytical x-ray analysis techniques developed in Latin America in respect to the developed countries?