XRF has become over the years a method of choice when dealing with elemental analysis of large quantities of samples. Geochemical analysis pushes the technique to its limits because of the large number of samples to be analysed as well as the lower limits of detection required for many trace elements of geochemical and economic importance. The Analytical Geochemistry Group at the British Geological Survey (BGS) has access to a wide variety of methods for instrumental analysis. Instrumental methods for inorganic analysis include x-ray fluorescence as well as DC arc emission spectrometry, atomic absorption spectrometry, inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). X-ray fluorescence, however, is the technique of choice when it comes to the routine analysis of large numbers of solid samples. The XRF section at BGS currently runs three sequential spectrometers (one PW1480 and two PW2400s made by Philips Analytical X-Ray). In this paper, some aspects of the method of sample preparation and the calibration of the spectrometers for the analysis of the trace elements are discussed.

The instrumentation developed for poly crystalline diffractometry using the storage ring at the Stanford Synchrotron Radiation Laboratory is described. A pair of automated vertical scan diffractometers was used for a Si (111) channel monochromator and the powder specimens. The parallel beam powder diffraction was defined by horizontal parallel slits which had several times higher intensity than a receiving slit at the same resolution. The patterns were obtained with 2:1 scanning with’ a selected monochromatic beam, and an energy dispersive diffraction method in which the monochromator is step-scanned, and the specimen and scintillation counter are fixed. Both methods use the same instrumentation.

In the last few years, at the Denver X-Ray Analytical Conference, the author and co-workers presented two papers which described the principle and applications of carbon analysis by X-ray fluorescence based upon a monochromatization technique consisting of total reflection and filtering. Instead of the wavelength dispersive method based on Bragg reflection, this monochromatization, combining total reflection by a selected mirror and an appropriate filter, offered an alternative approach for the purpose of increasing measured X-ray intensity. The analytical performance of quantitative determination of carbon content in steel, cast iron and coal were reported.

While conventional X-ray signal readout systems can be used in connection with the electron probe analyzer, new readout techniques can be applied with advantage, particularly for scanning procedures. Several novel techniques involving photographic recordings of oscilloscope tracings will be described. These techniques are applicable to area scanning (enhanced concentration method, concentration mapping with use of X-ray signals, and target current concentration mapping procedures) as well as line scanning. Combinations of area-scanning images with line-scan registration ate used for representing line-scan results.

By using operational amplifiers as signal adders, wavelength scans can be efficiently registered on a Polaroid photogram, with baseline indication and wavelength markers, in a single exposure. Another wavelength scanning technique registers the pulse height of the lines observed during the scanning operation, so that the order of reflection of the lines can be established. The use of an x-y recorder also offers advantages in the registration of line scans. Techniques for registration of multiple scans and for concentration mapping with the x-y recorder will be described.

The intense interest in production of heteroepitaxial quaternary structures of Gax In1-x Asy p1-y on InP for electro-optical telecommunications systems has Stimulated development of non-destructive techniques for their analysis. One of the most important is double axis X-ray diffractometry, a technique originally developed in the 1920s but only now coming into widespread use as a routine assessment tool. The basic theory is well treated by James and discussion of alignment errors are found in references cited by Fewster in a paper describing alignment procedures for the automated diffractometer manufactured by Bede Scientific Instruments of Durham, The application to III-V systems has been discussed by Tanner, Barnett and Bill.

Selected substances have been examined by X-ray fluorescence to determine the effect of particles or surface irregularities on the fluorescent intensity. The powdered substances examined were segregated into particle size classifications by the use of standard and micro sieves and ocular microscopic measurements. The substances thus classified were Iron, germanium, and titanium metals, copper furnace slag, and a cobalt molybdate catalyst. Graphical representations are used to characterize the relation between particle size and intensity. In certain cases the influence of particle size is expressed in terms of a calculated absorption length of the substance. The extent to which particle size in a powder affects the fluorescent intensity is a function of the absorption coefficients of the substance for the exciting and fluorescent X-rays, The effect on intensity of successive powder dilution of a high atomic number witha low atomic number substance has been measured. The results are of assistance in providing a concept of the structure necessary for maximum intensity. Little difference in the fluorescent intensity of an element is exhibited as between its dilution in a dry powder and in an aqueous solution, if the absorption properties of the two diluents are very similar. The effect of small surface irregularities in a metal exhibits no systematic relation to the fluorescent intensity.

Wavelengths and intensities are reported for the K series of magnesium, aluminum, and silicon, using primary excitation. Included in the tabulation for magnesium and aluminum are the diagram lines α1α2 and β and the nondiagram lines α', α3, α4, α5, and α6. Data are given for the Si K spectral lines α1α2, β, α3, and α4, Spectra are shown and line positions and intensities are detailed using both metal and oxide as the X-ray source. Significant differences are seen between metal and oxide spectra especially in wavelength and shape of Kβ, and large changes are noted in the intensities of some satellite lines. Spectra from a number of aluminum intermetallic compounds are discussed, including line positions, satellite line ratios, and line shape. It is shown that the spectra fall into three predictable groups; good conductors; poorer conductors; and semiconductors and insulators. Structurally similar compounds give similar spectra. For instance, line positions, shapes, and intensities are nearly identical for NbAl3 and TaAl3. It is not possible to correlate spectra with aluminum coordination number, and previous work using Kα, where secondary excitation was used, could not be reproduced using primary excitation. Possible reasons for this disagreement are discussed.

The effects of various combinations of divergence, receiving and Soller slits on x-ray measurements were investigated for Siemens-Halske and General Electric diffractometers. Influences of the following factors which also affect accuracy and precision of x-ray R.S. results were determined in addition: (a) parafocus versus stationary detector focusing geometry, (b) method of peak location, (c) LPA intensity correction, (d) diffractometer electronic stability and (e) elastic constants.

The optimum choiees of beam optics and factors (a-e) were defined with regard to aecuraey, precision and minimurn time for stress deterniination, on sharp and broad line speeimens of soft (annealed) and hardened steel and of annealed Cr-powder.

The lattice parameters of single-crystal SrTiO2 were determined by X-ray diffraction as a function of temperature from 4.2 to 300°K. Three significant regions were found: from 65 to 110°K a tetragonal modification, exists (c/a = 1.00056); from 35 to 55°K, line splitting consistent with orthorhornbic symmetry was observed, and at 10°K an anomalous maximum in the lattice parameter vs. temperature curve was found which suggested a third structure transformation. In the tetragonal region (at 78°K) the formation of a domain structure was observed with a polarising microscope. The low-temperature X-ray technique and X-ray cryostat are described.

Using protons in the MeV range as excitation source and a high resolution Si(Li) detector, X-ray emission spectroscopy is shown to be capable of analysing many elements with Z > 15 simultaneously at the 10-12 g level, This work discusses a theoretical lower limit of detection at moderate proton energies and gives examples of possible applications: analysis of the elemental composition of air-borne particles as a function of particle size, oil slick identification, and analysis of water and blood serum.

The principles of measuring surface stresses in metals by X-ray diffraction with commercially available equipment are well known. Two techniques of making stress measurement by X-ray diffraction now in general use are (1) X-ray diffractometer with electronic control panel and (2) back-reflection film camera.

The X-ray diffractometer technique has a number of important advantages over the film method, the major ones being accuracy and speed, but serious size and shape limitations are imposed on the specimen by the equipment: Because of its bulk and weight, specimens must be brought to it. The Airplane Division of The Boeing Company has capitalized on the advantages offered by the mobile backreflection film technique, especially with regard to specimen sizes and shapes. Results and techniques used, at Boeing for stress measurements in alloys of aluminum, titanium, and steel are presented. Experimental difficulties are discussed, and comparisons are made between results from the dirfractometer and backreflection camera, A portable darkroom and electropolishing unit are also presented which, with the X-ray unit, comprise a completely mobile stress-measuring facility.

With the development of soft X-ray sources by Henke, it is now possible to extend the range of quantitative analyses by X-ray spectrometry into the very light element range (magnesium through, boron). Techniques of specimen preparation, recognized as one of the most critical aspects of quantitative X-ray analysis in the heavier elemental ranges, present new problems, especially with the physically and chemically heterogeneous materials encountered in mineral and rock analysis. This paper presents the results of new tests extended into the light and very light element range. It is shown that most of the problems previously found are intensified as lower atomic number elements are considered; conditions of the specimen surface are critical and require precise control of particle size. In addition, significant absorption by relatively heavier elemental constituents, either in a separate phase or within the same phase, causes poor precision and is difficult to predict. Thus, the combination of matrix absorption within and between discrete phases, combined with the difficulty of grinding different phases to a uniform particle size, suggests that fusion techniques are required for hest precision. Without fusion, both scatter and bias are introduced through non-linear calibrations, with each calibration dependent upon specimen composition and particle size. It is concluded that only with nearly uniform specimens, where gross deviations are to be checked (e.g., process control) can ground rock powders be used with success in light element analyses.

The purpose of this paper is to summarize the theoretical basis and experimental techniques for application of the referenee intensity method to quantitative, multi-component analysis by x-ray diffraction (XRD). Detailed descriptions of the technique and formal error analysis are discussed by Davis (1978, 1980, 1981a, 1981b, 1981c).

The grazing-incidence X-ray diffraction (GIXD) method was employed to analyze two-layer thin films, which were the samples of Å lOO Å Au/500Å Cu/Si02 (substrate) and 250Å Cu/500Å Au/SiO2(substrate), which were prepared by the evaporation technique under the condition that the SiO2 substrate was at room temperature. Diffraction profiles were obtained at various glancing angles ( α ) and the data were analyzed as a function of α. The results were as follows : 1) Diffraction peaks were shifted to larger diffraction angles, because of the refraction of the incident X-ray beam. The angular shift has been approximated by the equation, α - α2- αc2)1/2, where αc is the total ref reflection critical angle of the material. 2) As a result of the correction of angular shift, the stress of the evaporated films was estimated to be null. 3) The broadening of the Cu diffraction peak and the enhancement of the Cu diffraction intensity occurred at angles near αc of Cu, due to the reflection of the X-ray beam at the Cu/Au interface.

Analyses performed have been to determine the feasibility of using pyrolytic graphite (PG) as an X-ray analyzing crystal. Pyrolytic graphite is formed by the pyrolysis of a hydrocarbon, which yields a hexagonal structure graphite with a high degree of anisotropy. After annealing, the anisotropic properties are enhanced even more. For most applications, the intensity and resolution are not as good as with, the best analyzing crystals; however, the extreme durability of pyrolytic graphite makes it a feasible X-ray analyzing crystal.

Periodic multilayers are ideally suited as high-reflectivity and wide-bandwidth Bragg reflectors. Their period can be matched laterally to the incidence angle so that for all points on the reflector, Bragg reflection is obtained for the same wavelength. Three major types of laterally graded multilayer optics were appJied to X-ray diffraction: (i) Parabolically curved multilayer mirrors were used to convert divergent radiation emerging from an X-ray source into a parallel beam. The parallel beam was applied in powder diffraction, grazing incidence diffraction, reflectometry, high-resolution diffraction, and protein crystallography, (ii) Elliptically curved multilayer mirrors focused the divergent radiation from the source into a line on the sample or detector. The high brilliance and small dimension of the focused beam make this mirror type suited for transmission diffractometry of capillary and fiber specimens, (iii) Planar multilayer mirrors were employed in divergent-beam optics. In Bragg-Brentano diffractometers, this mirror type can serve as a compact incident-beam monochromator for removing Kβ lines and Bremsstrahlung.

In most routine chemical analyses, a trade-off is made between quality of data and time required to obtain and analyze the data.In X-ray powder diffraction, identifications are normally made by Debye-Scherrer film methods or by medium speed (1-2°20/min.) diffractometry, with or without an internal standard. With one notable exception, the inherent precision of the Guinier camera geometry has been virtually ignored as too expensive or time consuming for routine work, or relegated to special projects. The accessibility of microcomputers, however, not only makes it economically and realistically feasible to automate the equipment previously used for special Guinier projects, but to extend the overall precision of observed d-spacings into the area of routine analysis. Search-match procedures benefit from the increased data precision to such an extent that they can be used routinely to propose the identity of major pure phases and release the analyst to concentrate on minor components and impure phases which may be subject to lattice constant shifts.

Two methods of obtaining polarized x-rays for fluorescence experiments are discussed. Compton scattering from a low-Z scatterer is the usual method used in such experiments. The polarization of x-rays undergoing anomalous Borrmann transmission in a dislocation-free crystal is also described and preliminary results are presented. Approximate expressions, useful for comparing scatter-polarizing systems, are derived for the dependence of scatter rejection and fluorescent efficiency on two scattering-system parameters: the thickness of the scattering polarizer and the geometric limit to solid angles and angular divergences in the system.

The principle to utilize total reflection of the primary X-rays in fluorescence analysis is known since a lot of years. Nevertheless, analytical chemistry did not profit from the inherent advantages of the method for a long time. The main reason for this failure was the lack of instruments which were easy to use in practice. A few years ago, however, the development of a proper mechanical design and of adapted sample preparation techniques led to commercially available spectrometers which throughout fulfill the demands for routine applications. Since then the utilization of Total-Reflection X-Ray Fluorescence Analysis (TXRF) has increased rapidly. The scope of work is meanwhile widespread over environmental research and monitoring, mineralogy, mineral exploration, oceanography, biology, medicine and biochemistry. Accordingly, numerous matrices have been handled.

A review of the literature has shown that two major techniques are used to determine stress/strain in thin film structures: curvature measurement technique and internal stress measurement by the traditional sin2ψ technique. However, to date, there is no published comparison of the results from both techniques when they are applied to a given specimen.

In this paper we compare both methods theoretically and experimentally. We show that, while in some cases similar information is obtained from both techniques, there are cases where the two measurements give different results. We will show that, in such cases, the two methods can be complementary. Thus, they can be used to yield a more complete description of the total stress/strain tensor in the material.