Minor amounts of rare-earth elements (0.01 to 1.0%) in high-purity rare-earth oxides may be determined by a fluorescent X-ray procedure. The analysis of high-purity yttrium, cerium, praseodymium, neodymium, and samarium is described. Basic to the method is accurate determination of spectral line intensity above background. Sample and standard preparation, choice of analytical lines, and utilization of a helium path to increase X-ray intensities are discussed. Precision and accuracy were evaluated by analyzing samples of known composition. The average of five separate determinations showed an average error of about 10 per cent.

The magnetic crystal disrortion of weakly ferromagnetic α-Fe2O3 was investigated by x-ray diffraction techniques. Here crystal distortion is taken as the temperature dependent changes of lattice constants and thermal expansion coefficients. Moreover, the oxygen position parameter and the carbon-oxygen distance of MnCO3 were determined.

The lattice constants and thermal expansion coefficients of α-Fe2O3 were measured from room temperature down to 243°K. The crystal distortion, as measured by the changes in lattice constants, thermal expansion coefficients and axial ratio, was found to be highly anisotropic. The co hexagonal lattice constant was influenced very slightly by magnetic distortion; it changed only by 0.01 percent between room temperature and the Morin temperature of 254°K. On the other hand, the ao lattice constant changes by 0.11 percent between room temperature and the Morin temperature. The thermal expansion coefficients of the lattice constants showed a similar contrast. The co coefficient was found to be independent of temperature from room temperature down to the Morin temperature. However, in the same temperature range, the ao coefficient showed an anomalous increase with decreasing temperature. In addition, the ao coefficient showed an infinite discontinuity at the Morin temperature.

The change in the axial ratio with temperature suggests that the net weak ferromagnetic moment of α-Fe2O3 reaches a maximum at 275°K.

The oxygen position parameter, x, in MnCO3 as determined from two reflections has a value of 0.2702 ± 0.001. The carbon-oxygen distance as calculated from the lattice constants and the oxygen position parameter is 1.29 ±0.002 Å. This value is another confirmation of the Pauling theory of the resonating carbonate structure.

We have recently described an automated powder diffractometer, the APD-3500, in which a small (4K x 18 bit) minicomputer is utilized for hardware control and data processing. Among the software programs developed for this system is a “Peak Search“ routine which is designed to record a diffraction pattern with optimum, use of scanning time and to give output directly in J.C.P.D.S. Powder Data File Format. Optimum use of scanning time is achieved by a double-pass System in which a first (rapid) pass is made to establish significant data.

A second routine is a “Line Profile” routine which gives the choice of rapid slewing or slow Step scanning of the goniometer between selected angular ranges. The routine thus allows the controlled stepping of the goniometer between selected angular ranges giving incremental and integral, background corrected counts. An automatic internal and/or external calibration capability makes this particular mode ideal for quantitative analysis.

Polarized x-rays are used to excite samples of any kind and shape to emit characteristic radiation. In the appropriate geometry, where source-sample-ED detector are in any orthogonal position to each other, the exciting poLarized x-rays will be practically not scattered from sample and substrate into the detector. This reduces the background considerably and hence improves the lower limits of detection. The production of intensive polarized x-rays is done by using a single crystal-where Bragg reflection occurs at an angle 2 θ = 90° instead of amorphous low Z scatterers. The result is a linear polarized and monochromatic beam. The use of curved crystals instead of plane single crystals further increases the intensity of the exciting radiation. The lower limits of detection attainable with the recently constructed compact polarizer device are in the sub ppm range or in absolute amounts around 150 pg for medium Z elements.

The mass absorption coefficient (μ) of a weakly absorbing solid material may be measured by either the transmission or the reflection method. The latter typically employs a crystalline substrate and the diffraction method, measuring the transmission of the diffraction peak(s) of the substrate through the analyte. Compressing or compacting a powdered sample is not required when the reflection method is used.

Use of Chelex-100 impregnated filter membranes for preconcentration of uranium in ground-water samples for XRF analysis leads to lower processing time, sample size, and detection limit than achieved in a batch extraction process. Data is presented, for potential effects of iron and organic matter in natural waters upon the recovery of uranium when using Chelex-100.

Quite recently there has been commercially developed a series of high-alloy steels, on new compositional bases, which possess 3 very desirable combination of unusually high strength, good ductility, and toughness even at comparatively low temperatures. At the same time, research with mechanical working procedures, combined with optimum heat-treat considerations, have produced with several older, more conventional steels, strength levels of high orders of magnitude. Each of the considered materials is capable of yield strengths approaching or exceeding 300,000 psi, corresponding to elastic strains of about 1%.

This paper is concerned with the development and evaluation of workable X-ray stress analysis procedures to be employed to measure, with a good degree of accuracy, high elastic strains. The materials selected include maraging steels, ausformed steels, and cold-drawn A.I.S.I. 4340 steels.

Of the various possible X-ray techniques which were considered, very satisfactory results were obtained by the use of the two-exposure method. A special fixture was designed and constructed to allow uniaxial straining of test specimens while in the X-ray unit. Imposed strains were measured directly by strain gauges mounted on tbe specimen. Simultaneously, strains were measured by the use of chromium radiation filtered with vanadium foil. The peak resolution obtained was very satisfactory with a peak to background ratio of approximately 4:1 for the {211–121} martensite doublet used to measure the shift in peak location between the normal and oblique exposures. Because of the widths of the peaks involved, it is impossible to precisely specify the angular position of a given peak by inspection of the usual recorded trace. A counting technique, combined with a least-squares curve-fitting procedure involving five points, was very satisfactory for precisely locating positions of maximum intensity, Superior results were obtained when a multiplicative correction factor proposed by Koistinen and Marburger was applied.

Position-sensitive detectors (PSD's) are commonly available for X-ray diffraction, where they are used in the angle dispersive mode at fixed wavelength λ. They are sensitive to the scattering angle 2Θ. The resolution of such instruments is determined by the physical properties of the detector, and, of course, the distance from the sample. Using continuous radiation solid state detectors (Ge, Ge(Li), Si(Li)) are sensitive to energy (equivalent to λ) at fixed scattering angle 2Θo, They are being used for X-rays, especially with synchrotron radiation. Because X-rays travel with the speed of light, those two techniques cannot be combined. Thermal neutrons, on the other hand, are comparatively slowly traveling particles (2200 m/s at 300 K) and consequently time-of-flight (TOF) instruments with choppers at continuous neutron beams are known for a long time; they are being used as well for diff-actomet! y as for inelastic scattering.

The development of powder-pattern-fitting techniques greatly changed the methodological aspect of materials characterization using powder diffraction data. Pencil and ruler are going out of use in modern powder data analysis, and present-day materials scientists hit a keyboard and manipulate a mouse of computer for deducing the final parameters of the model, which gives the best fit of calculated pattern to the observed one on a CRT screen. Computer software is now widespread, and the success in materials characterization becomes much dependent on their availability.

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.

Preferred orientation in polymers has been studied by preparation of pole figures. The diffraction data are collected on punch tape under the control of a programmer for the orienter which permits step wise or continuous scanning. A computer is programmed to prepare the data for an off-line automatic curve plotter. Several projections are available.

A single function for the elimination of errors in precision lattice parameter determination has not been developed for the Bragg-Brentano x-ray diffractometer method, because of the different angular dependencies of the systematic errors. A review of the error functions shows that all but one can be calculated from the instrumental settings and known properties of a sample under investigation. The residual sample displacement error can be then be eliminated by using extrapolation plots or computer methods to correct the data to cosθcotθ plots. The slopes of cosθcotθ plots can also be used to align high temperature furnaces and low temperature cryostats mounted on x-ray diffractometers.

This paper deals with soft X-ray spectra of compounds which have one or more spectator hole(s) in the valence orbitals. The aim is to give a simple picture of the complicated chemical effects and to describe implications of the chemical effects to know the chemical state from the complicated spectra of materials. The first example of the system which has a spectator hole in the valence orbital is the intensity modifications of the shake-off satellites (KM-→LM) in chlorine Kα spectra. The second example of the system which has spectator holes in the valence orbitals is the multiplet structure of Lα spectra of the transition-metal compounds. It is described that the chemical effects of these two systems are clearly interpreted by the avoided crossing [1] of the molecular orbitals, one of which has a localized hole. We also describe the systems which have no spectator holes. The interpretation of the X-ray spectra of these systems are easy by a molecular-orbital calculation at the ground state.

The following study is an evaluation of several different types of instrumentation available for use in powder x-ray diffraction work. The particular units used are those at the Dow Chemical Company x-ray diffraction lab. The variety of instrumentation allows analyses from routine phase identification to more specialized work such as low-angle x-ray diffraction of polymers and high-resolution analysis for cell parameter refinements.

The purpose of this work is to compare the relative capabilities of these different instruments under typical day-to-day operating conditions. While not a comprehensive study, the conclusions drawn should be applicable to powder x-ray diffraction in general.

X-ray powder pattern line intensities were measured for the (Cr, Re)σ and (Re, Fe)σ phases by a step-scanning diffractometer, using CrKα radiation, scintillation counter, and a pulse height analyzer. The measured intensity ratios for all available pairs of adjacent lines were compared by means of a computer with the corresponding calculated intensity ratios based on approximately 1800 different ordering schemes for each alloy. The results showed ordering in both alloys, and indicated that the ordering was based on atomic size. These results are different from those obtained previously by Kasper and Waterstrat (no ordering), and by Ageyev et al. [In (Cr, Re)σ the Cr atoms are preferentially in large coordination number positions.]

The instrumentation for measuring x-ray yields from laser produced plasma is described. This new type of calorimeter is composed of a silicon detector, a charge-sensitive preamplifier and an analog-to-digital readout scheme for multiplexing up to ten detector outputs.

X-rays interacting with the detector produce hole-electron pairs in proportion to the total energy lost in the detector (∼1012 eV). In this application the detector can be characterized as a solid-state ionization chamber. The detector signal is coupled to a charge-sensitive preamplifier which generates a voltage pulse proportional to the x-ray energy absorbed. In this way the x-ray energy is measured by “direct conversion” rather than measuring the temperature rise due to an energy flux.

Several calibration methods and empirical formulae have been developed so far for analyzing materials quantitatively in XRF spectrometry. Many of them require reference samples to determine the relationship between the characteristic intensities of the elements and their concentrations. In order to eliminate empirical and semiempirical procedures, the fundamental parameter method (FPM) has been developed, which is one of the most helpful evaluating tools in quantitative XRF analysis. Some interpretations of this approach have the advantage that no standard samples are needed. The simultaneous application of FPM and polychromatic excitation demand an exact mathematical description of the primary spectral distribution as well as the efficiency function of the detector system.

The high-temperature continuous X-ray diffraction technique has been used at the University of Illinois for several years in our investigation of structural transformations and the development of phase minerals as natural materials are heated. Of particular interest are the effects which chemical impurities have on predicted structural transformations at elevated temperatures.

The formation of mullite and beta-cristobalite as they develop from the clay mineral kaolinite is examined by continuous X-ray diffraction up to 1450°C, and the influence of added impurities either to enhance or to retard nucleation of these phase minerals is shown. The 2θ range containing diagnostic peaks of both the initial material and of the transition and phase minerals which develop on heating was continually traversed, thus providing a constant record for comparing structural changes vs. temperature.

The furnace used is described in detail, and the effects of added impurities on kaolinite transformations are evaluated to show their importance in controlling the thermal history of a natural material under nonequilibrium conditions.

A simple method for high-resolution measurement of surface misorientation in electronic materials is introduced. The technique combines laser optical alignment with double-crystal x-ray diffraction to yield a typical sensitivity of better than 1-2 arc sec. The technique can also be used to make corrections in spectrometric measurements in which commonly ignored rocking - curve errors may be significant.

We describe a new X-ray fibre diffractometer, consisting of a commercial X-ray sensitive video camera coupled to a conventional 3-circle goniometer in place of a more traditional single-point detector. The active element of the video camera is a charge-coupled device (CCD). Diffraction images, obtained at various goniometer settings, are transformed into reciprocal space, and combined to give a complete section through the origin and parallel to the symmetry axis of cyiindrically averaged reciprocal space. A greater density of measurements is needed in the vicinity of the reciprocal fibre axis in order to avoid information loss due to the curvature of the Ewald sphere. The pros and cons of using CCD's as X-ray detectors are discussed and sample results from polymer fibres are shown.