For many years the International Centre for Diffraction Data has sponsored round robins covering various aspects of X-ray powder Diffraction with the objective of illuminating and understanding current practices and problems associated with, the analysis of diffraction data. As computer analysis of diffraction data becomes ever more sophisticated, analytic capabilities are extended and the performance, not only of the instrumentation must be checked, but also that of the software which converts the measured data into useful results. In recent years, therefore, we have personally participated in a cell parameter round-robin, a d-spacing round-robin, a peak hunting round-robin, and, most recently, the present intensity round-robin and a line profile round-robin. Still others are in progress or being planned.

Total reflection X-ray fluorescence (TXRF) analysis of “low Z” elements, Ti, Fe, Ni, Cu, Zn and “high Z” elements, Zr, W, Au, Pb, are required for micro scale semiconductor device production processes. In the past, the W–Lβ X-rays have been used for the analysis of S to Zn.

This paper describes a new three crystal monochromator coupled with a gold direct-drive rotating anode target. This development has produced significant improvements in the sensitivities and LLD's for all measured elements. The monochromator makes the Au Lα (9.71 keV), Au Lβ (11.44 keV) and Au Lγ (13.33 keV) available for routine use in TXRF analyses. The Au Lα X-ray is best used for the lower Z elements, Na to Cu. The best result for W, Cu and Zn are obtained with the Au Lβ X-ray. This is the result of both increased peak intensity and lower background. For the heavier elements, such as Au and Pb, the Au L X-ray yields intensities 100 times higher than what has been achieved in the past.

The first in vivo x-ray fluorescence measurements of lead in bone used y-rays from a 57Co source to excite Pb K x-rays. Later systems used γ-rays from 109Cd to excite Pb K x-rays or polarized x-rays to excite Pb L x-rays. All three approaches involve an extremely low effective dose to the subject. Of the two K x-ray techniques, 109Cd is more precise and more flexible in choice of measurement site. Pb L x-ray fluorescence (L-XRF) effectively samples lead at bone surfaces, whereas Pb K x-ray fluorescence (K-XRF) samples through the bulk of a bone. Both the polarized L-XRF and 109Cd K-XRF achieve similar precision.

Renal mercury has recently been determined using a polarized x-ray source. Both renal and hepatic cadmium can be measured using polarized x-rays in conjunction with a Si(Li) detector. Platinum and gold have been measured both by radioisotopic source excitation and by using polarized x-rays, but the latter is to be preferred.

Applications of Pb K-XRF have shown that measured bone lead relates strongly to cumulative lead exposure. Secondly, biological half lives of lead in different bone types have been estimated from limited longitudinal data sets and from some cross sectional surveys. Thirdly, the effect of hone lead as an endogenous source of lead has been demonstrated and it has been shown that a majority of circulating blood lead can be mobilized from bone, rather than deriving from new exposure, in some retired lead workers.

Characteristic soft x-ray emission lines created as a result of low energy (10-100keV) positive ion excitation of a target material has been applied to the study of thin films of oxygen that form naturally on metal surfaces. The specific metals investigated were aluminum and nickel aa well as a number of their corresponding alloys.

Low energy positive ions are well suited as projectiles for the study of thin films in that they have low penetrating powers, yet produce high x-ray yields for K-, L-, and M-shell elemental x-ray lines. Perhaps the most important feature is the fact that no background bremsstrahlung continuum x-radiation is generated in the slowing processes of the ions. Exploiting the advantages of these facts, a special high sensitivity detection technique has been developed for the soft x-ray analysis of the constituents that make up a particular thin surface film.

The physical basis for thickness and atomic density measurements of thin surface films by positive ion excitation are discussed. Calibration data are presented for thin films of known thickness and composition establishing the sensitivity of the method for the measurement of the elemental atomic densities of thin films down to a few monolayers or approximately 10 Å in thickness. Finally, the results of the analysis of oxide surface films of aluminum, nickel and some of their alloys are presented and discussed.

The objective of this continuing program is to gain an understanding of the mechanisms and principles governing the formation of oxide surface films on metals with the basic goal of producing new alloying techniques for metal passification in a saline environment.

Uniformity of particle size is most critical iti both X-ray spectrographic and diffraction samples. This is especially true when there are both hard and soft materials in the sample. The soft material reduces to a smaller particle size and therefore presents a great density and area to the X-ray beam. Accurate quantitative determinations are most difficult under these clrcum s tances. This paper decribes a means of grinding to a more uniform particle size and presents graphic data on the effects of particle-size variation.

A requirement exists in the aeronautical industry for measuring temperature non-invasively in critical components, such as the turbine disc in an operating engine. Neutron diffraction, unique among nuclear techniques, offers the possibility of measuring both temperature and strain within an operating engine by virtue of the high penetration of neutrons through industrial materials. Static diffraction experiments on Waspaloy and Ti6A14V showed, by comparison with thermocouples, that both the diffraction peak position and the peak intensity can measure the tempeiaturc to within ±6 K aL 800 K. Measurements on a rotating Waspaloy disc, heated from its rim, showed that temperature gradients could be determined accurately by lattice parameter measurements. The large grain size in Waspaloy prevented accurate peak intensity measurements in this dynamic test. Finally, the structures within a small Pratt & Whitney engine in its equatorial plane were mapped by mounting the engine on an X-Y translator on the diffractometer and moving it through a grid of positions. Possible future directions in the field will be discussed.

An x-ray spectrometer with experimental results is herewith described using a radiosotope source Fe55 having a halflife of 2.6 years. As a result of the disintegration, the managanese x-rays are capable of exciting fluorescent x-rays of such elements as sulfur, chlorine, potassium, calcium, scandium and titanium in aqueous solutions. These elements with the Ka wavelengths ranging from 5.3729 Å to 2.7496 Å may be designated as between the very soft x-rays on the one hand and the hard x-rays on the other. The x-ray spectrometer presently described has achieved a resolution of 136 ev, FWHM.

Simultaneously, these elements have also been quantitatively determined by conventional x-ray fluorescent spectrometers. Since one of the spectrometers is designed to operate in vacuum as well as in helium or air, determination of sulfur, potassium and calcium were carried out in vacuum. Determination of chlorine was carried out in a helium atmosphere, Calcium, scandium and titanium were determined in air with an air-path spectrometer.

In the present study aqueous solutions containing these elements were used. The use of aqueous solutions has the inherent advantages of being homogeneous and free from effect of particle size.

As early as 1974 cracking was observed in the austenitic stainless steel piping systems of several Boiling Water Reactors [1,2]. Failure analysis indicated that the cracks developed through intergranular stress-corrosion cracking and an active interest in residual stress measurement methodologies developed. This paper describes the procedures and demonstration testing employed to provide absolute residual stress measurement, nondestructively, on the inside surface of pipe specimens. A Ruud-Barrett position sensitive detector (PSSD)* was used to build an EPRI pipe stress analyzer which was developed for these residual stress measurements [3,4].

At the present time there is considerable interest in the use of adhesive bonded joints for structural applications. The design of such joints is based mostly on finite element calculations and failure tests rather than on strain or stress measurements. To our knowledge no measurements have been made of stresses at or near the adhesive/adherend interface (where many bond failures occur) because of difficulties with accessibility. The purpose of this work was therefore to try to make such measurements using X-ray diffraction.

The approach taken was to gain access to the bond by making one of the adherends in a single lap joint to be relatively transparent to X-rays and the cither relatively opaque. Incident X-rays then penetrated the first adherend and the adhesive and were diffracted from gains in the second adherend adjacent to the adhesive/adherend interface. Stresses resulting from curing of the adhesive were determined first, after which a load was applied and the stresses redetermined.

A compact, high-intensity pulsed soft X-ray system has been used to study the response characteristics of a plastic scintillation phosphor (NE-102). In particular, the decay characteristics of this phosphor plated on one surface with a thin (<1000 Å) layer of aluminum were investigated. Although, absolute calibration of the X-ray source had not been performed, estimates of X-ray scintillation efficiency were obtained, using two separate methods, which were in agreement to within a factor of two.

The primary purpose of this cursory program was to establish the validity of transferring calibration data from plated to unplated NE-102 scintillators employed in a photometric recording system. The results of the ensuing investigation indicated the equivalence of the two, but revealed several interesting and unsuspected phenomena. These were (1) an apparent scintillation light reflectance component of zero from the plated aluminum “mirror” surface, (2) a change in pulse waveform from electron beam input to scintillation light output, and (3) a 90-nsec delay between electron beam and photomultiplier signals. The methods employed in obtaining and verifying these data are subject to errors from uncertainty in the characteristics of several components employed in the experimental setup. These uncertainties and other measurement errors caused independent estimates of the external scintillation light efficiency to range from 0.1 to 0.2 %.

Other potential applications of a pulsed soft X-ray system to measurement problems in industry and research include dynamic studies in the fields of X-ray crystallography, instrumental methods of materials analysis, and radiography of low-density subjects.

Wires of 18 different metals were exploded in nitrogen by the discharge of a 20-μF capacitor bank charged to 10 kV. The resulting aerosols were collected under nitrogren on membrane e filters, which were mounted on glass slides and used directly in the sample holder of a recording X-ray diffractometer. The X-ray data were analyzed to determine the composition and approximate crystallite size of the particulates produced by the wire explosions in nitrogen and subsequent exposure to air.

Nitrides are found as reaction products from the explosion in nitrogen of aluminum, iron, indium, tantalum, thorium, uranium, tungsten, and zirconium. No nitrides were detected in the samples from cadmium, copper, magnesium, molybdenum, lead, and tin explosions, although such nitrides are known to exist; and the aerosols produced in nitrogen by the explosion of silver, gold, molybdenum, platinum, and tin consist almost entirely of metal particles. Oxides are attributed to contamination of the nitrogen or exposure of the samples to air.

Most of the crystallites observed are less than 1000 Å as determined from X-ray line broadening find confirmed in some instances by electron microscopy. For the UN2 and ThO2, crystallite sizes of the order of 130 Å and 50 Å, respectively, are observed. In samples comprised of a mixture of phases, the constituents usually have different mean crystallite sizes. The crystallite size is not affected dramatically by the ambient nitrogen pressure or voltage used.

As the Environmental Protection Agency adds ever more sites to the National Priorities List for Superfund clean-up, there is a tremendous need for a fast method of screening for contaminants. In the case of inorganics, we can apply field-portable X-ray fluorescence technology.

With commercially available field-portable X-ray fluorescence equipment using in-situ measurements we can quickly screen a site (hundreds of measurements), input the data to a portable computer, process it, and print a colored concentration isopleth map of the contaminant of interest, all in realtime.

The in-situ measurement approach pioneered by Lockheed is the key to rapid screening capability. Problems arising from particle size distribution, soil heterogeneity, and bulk density are minimized by employing site-specific standards in the construction of our calibration curves. Inherent in these site-specific standards are all the matrix problems which occur in the routine samples.

The strength of field-portable X-ray fluorescence technology is the accuracy of analysis above the quantitation limits. The difficulty in measuring low concentrations near the detection limit is the weak point of field-portable units.

NOTICE: Although this research was funded in part by the U.S. EPA through Contract 68-03-3249 to Lockheed Engineering & Sciences Company, it has not undergone Agency review and does not necessarily reflect Agency policy.

A flow proportional counter for ultrasoft x-ray applications has been constructed and used to measure proportional counter parameters in the ultrasoft x-ray region at atmospheric and subatmospheric pressures for counting gases of P-10 and methane. We find that at atmospheric pressures the parametrization given by Zastawny for describing gas amplification in proportional counters applies and have measured values for the parameters for P-10 and methane. For subatmospheric pressures the Zastawny parameters are inadequate. A new parametrizatlon is required. In addition, the linearity of the detector for x-rays of energies of 15 KeV to 0.5 KeV was measured for pressures ranging from 750 Torr to 150 Torr and found to be excellent in all pressure regions.

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.

The problem of background radiation in X-ray fluorescence trace element analysis of fused-glass iron ore samples is addressed. A first-order model of coherent and Comptcn scattering with primary absorption is presented and used to correct measurements. Overlap coefficients for elements in iron ores are presented. The importance of these corrections is demonstrated. The accuracy achieved with X-ray measurements after background corrections compares well with the accuracy of chemical analysis.

For the generation of high temperatures in X-ray and neutron diffraction experiments various techniques such as resistance heating, radiation heating, induction heating and gas flame heating have been applied (Aldebert, 1984). Mirror heaters usually employ some kind of focussing geometry to concentrate the radiation emanating from the heating element onto the sample: Two large parabolic mirrors focussing heat radiation from a carbon arc were used by Stecura (1968) to reach sample temperatures up to 1700°C. Hubert et al. (1974) used radiation from a short arc xenon lamp focussed by two parabolical mirrors to reach sample temperatures of 3200°C.

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.

Calculated patterns play an essential role in X-ray powder diffraction analysis. This paper gives examples of their use in qualitative analysis for evaluating and supplementing reference patterns in the ICDD Powder Diffraction File (PDF), in quantitative analysis for calculating Reference Intensity Ratios (RIRs), in ceil parameter refinements for indexing of low-symmetry/large unit cell diffractograms, in powder pattern determination for validating intensities and recognizing preferred orientation, in new materials synthesis for verification of structure type and phase purity, and for modeling the effects of solid solution substitution.

Modern powder diffraction employing computer-controlled diffractometers now allows quantitative analytical methods to use the whole diffraction trace rather then only individual peaks. Two such methods are in common use the Rietveld method which refines the crystal structures of the component phases as part of the matching calculation, and the patternfitting method which uses reference patterns from a database. Potential accuracies of these methods seems to be around 1 % absolute. The most severe limitation on the potential accuracy of these methods is particle statistics, which has been reviewed in considerable detail.