Presented here is a report on the development of practical techniques for laboratory spectroscopy in the 5 to 150 A wavelength region as may be applied, for example, to light element and surface state analysis, high temperature plasma diagnostics and to the design and calibration of x-ray astronomy measurements.

High-temperature X-ray diffractometer measurements by the Bureau showed that alpha-alumina expands anisotropically with expansion parallel to the c axis approximately 10% greater than that parallel to the a axis. Thermal-expansion characteristics of four different alumina samples were determined up to 1200°C; the results are presented in both tabular and graphical form. The combined random and systematic errors in the measurements are considered less than 3% above 500°C and approximately 2% at 1000°C. No differences in expansion were observed between the samples or between the heating and cooling cycles.

Critical evaluation of the literature showed that published values for thermal-expansion coefficients of single crystals vary over a range of 40% (relative values) and disagreement concerning whether expansion of alpha-alumina is isotropic or anisotropic. Systematic and experimental errors were found to be the principal factor for the variation in results, rather than differences in measuring techniques or in samples.

Published values for polycrystalline aggregates also varied. Two laboratories reported values 20–30% lower than those of the Bureau of Mines, but two other laboratories agree with the Bureau within 3–5% above 500°C.

Residual stresses are found in the majority of multilayer thin film structures used in modem technology. The measurement and modeling of such stress fields and the elucidation of their effects on structural reliability and device operation has been a “growth area” in the literature, with contributions from authors in various scientific and engineering disciplines.

In this paper a review of the definitions of the residual stresses used by the authors in the various disciplines is presented and the mechanisms by which residual stresses may form in thin film systems is discussed.

The wavelength of the characteristic X-radiation for the lighter elements is not constant but is a function of valence state and to a much lesser extent is a function of co-ordination number.

Commercially available X-ray fluorescence equipment is used in detecting shifts in the characteristic radiation for aluminum, sulfur, chlorine, titanium, vanadium and iron. The greatest shift is found in the case of chlorine where, using the NaCl analyzer, a shift of nearly 0.2° 2 θ is obtained in going from the Cl− in cholorides to the Cl+7 in the perchloratc. The wavelength of the Al+3Kα varies slightly as a function of co-ordination number.

Examples are given for using these phenomena in studying minerals and other compounds. The feasibility of extending the study to both heavier and lighter elements is explored.

Recently, the remains of a giant Cretaceous Sauropod (~150 My old) were discovered in the Morrison Formation west of Albuquerque, New Mexico. This dinosaur, tentatively named Seismosaurus, was found in an exceptional state of preservation. Although it has been known since the 180Q's that fossilized bone is often composed of the mineral apatite, very few studies have been conducted to characterize farther the fossilized material. In an effort to gain insight into the state of preservation and Hie processes occurring in the bone since deposition, apatite in bone from Seismosaurus was compared with that from a contemporary elk from the Jemez Mountains, New Mexico, and with well-crystallized mineral apatite using X-ray powder diffraction and profile analysis techniques. Crystallite size/strain analyses were conducted using the Scherrer equation, the Warren-Averbaca and single-line methods, and the Rietveld method using the program GSAS. Heating the contemporary elk bone produced a decrease in the full-width-at-half-maximum (FWHM) of the reflections in the diffraction pattern. This decrease in FWHM is due to a decrease in microstrain along with a minor increase in crystallite size. Results from crystallite size/strain analysis show that both Seismosaurus and contemporary elk bone crystallites are elongate parallel to the c-axis. However, Seismosaurus bone crystallites are larger (-20-65 nm) with less strain than the contemporary elk bone crystallites (-8-20 nm), suggesting that if elk bone is an appropriate analog, then Seismosaurus bone must have undergone recrystallization.

Undoubtedly the most important applications of X-ray fluorescence spectrometry (XRF) have been in the analysis of major elements where the technique provides a unique method of measuring the concentration of all elements having Z > 10 with extremely good precision in a wide range of matrices. However, XRF is in addition a powerful method for trace element analysis. In this discussion, the principles of the method for the trace element analysis of rocks are outlined, its capabilities are summarized, and the advantages and disadvantages of the technique are pointed out.

Polarized x-radiation produced by scatter at 90° from boron carbide is shown to be a superior excitation source for the measurement of trace elements by energy dispersive x-ray fluorescence. In a close-coupled system which uses a high power x-ray tube as the primary source, the losses due to the geometric requirements and scattering efficiency of the polarizer can be more than compensated. With the system described here which uses a Mo anode x-ray tube, detection limits for the element between K and Sr in NBS orchard leaves are approximately 2 to 4.5 times lower using polarized excitation in comparison to direct excitation, and about <1 to 3 times lower in comparison to secondary excitation.

Lead stearate and lead lignocerate multilayer soap-film structures are used to disperse the K emission lines of boron and beryllium respectively. Data are presented showing the dependence of the peak height and half-width on the number of layers in the lignocerate structure. Spectra are presented and compared for the pure element and several compounds of each element. Both electron and X-ray excitation are used. Detection is by a thin-window flow-proportional counter.

From pole figure data, the orientation of a crystallographic direction R in any reference direction Q in a sample can be quantitatively expressed by the average <cos2σ>, where σ is the angle between Q and R in a crystal. In general, <cos2σ> can be evaluated in terms of the experimental averages <cos2ϕhkl> whereϕhkl is the angle between Q and the normal to the (hkl) planes. The number of independent <cos2ϕhkl> measurements needed varies from one to five depending on the crystal system, hkl indices, and other factors discussed. Experimental techniques found useful for measuring <cos2φ> are described.

A position-sensitive proportional counter suitable for the X-ray stress measurement has been developed and residual stresses were measured with an apparatus that uses this PSD system. The counter was designed to have a good angular resolution over the counter length for the diffracted X-ray beam and high counting rates. The mean angular resolution measured was about 0.2° in 2θ (FWHM) at 200 mm, and the maximum allowable counting rate reached about 40,000 cps.

The time required for the data accumulation was shown to be 1/10 to 1/30 of the time required with a standard diffractometer.

Accuracy, or how well a measurement conforms to the true value of a parameter, is important in XRD analyses in three primary areas, 1) 26 position or d-spacing; 2) peak shape; and 3) intensity. Instrumental factors affecting accuracy include zero-point, axial-divergence, and specimen- displacement errors, step size, and even uncertainty in X-ray wavelength values. Sample factors affecting accuracy include specimen transparency, structural strain, crystallite size, and preferred orientation effects. In addition, a variety of other sample-related factors influence the accuracy of quantitative analyses, including variations in sample composition and order/disorder. The conventional method of assessing accuracy during experimental diffractometry measurements is through the use of certified internal standards. However, it is possible to obtain highly accurate d-spacings without an internal standard using a well-aligned powder diffractometer coupled with data analysis routines that allow analysis of and correction for important systematic errors. The first consideration in such measurements is the use of methods yielding precise peak positions, such as profile fitting. High accuracy can be achieved if specimen-displacement, specimen- transparency, axial-divergence, and possibly zero-point corrections are included in data analysis. It is also important to consider that most common X-ray wavelengths (other than Cu Kα1) have not been measured with high accuracy. Accuracy in peak-shape measurements is important in the separation of instrumental and sample contributions to profile shape, e.g., in crystallite size and strain measurements. The instrumental contribution must be determined accurately using a standard material free from significant sample-related effects, such as NIST SRM 660 (LaB6). Although full-pattern fitting methods for quantitative analysis are available, the presence of numerous systematic errors makes the use of an internal standard, such as a-alumina mandatory to ensure accuracy; accuracy is always suspect when using external-standard, constrained-total quantitative analysis methods. One of the most significant problems in quantitative analysis remains the choice of representative standards. Variations in sample chemistry, order-disorder, and preferred orientation can be accommodated only with a thorough understanding of the coupled effects of all three on intensities. It is important to recognize that sample preparation methods that optimize accuracy for one type of measurement may not be appropriate for another. For example, the very fine crystallite size that is optimum for quantitative analysis is unnecessary and can even be detrimental in d-spacing and peak shape measurements.

Smectites are clay minerals that expand and contract dramatically in response to changes in water vapor pressure. The expansion/contraction behavior of smectite has considerable importance in engineering applications (such as the stability of building foundations and the integrity of clay barriers) and affects hydrologic properties. To understand this behavior we have analyzed several purified, homoionic smectite standards over a wide range of relative humidities using X-ray powder diffraction (XRD) and a new computer-automated humidity-control system.

Humidity was controlled by mixing dry N2 with H2O-saturated (“wet”) N2 produced with a gas-washing bubbler held in a constant-temperature bath set at 35°C. Mixing of wet and dry N2 was controlled with automated MKS mass-flow controllers.

Energy dispersive x-ray fluorescence is an established and versatile tool for measuring major and trace elements in virtually any kind of solid or liquid specimen. The usefulness of the method could he extended even further if the time of analysis for multicomponent samples could he reduced. In other words, we desire to analyze a wide range of elements with detection limits at least as good as obtained when the excitation conditions are optimized for a specific element or narrow range of elements. A major impediment to achieving this goal when analyzing bulk, low-Z materials is the scatter of source radiation into the detector by the specimen being analyzed. The adverse effects of the scattered radiation are its contribution to the background signal (i.e., “noise“) and its overwhelming contribution to the limited counting rate of the system electronics.

In the course of work, on the CaO-Nb205-Si02 System, a series of compositions on the Ca0-Nb2-05 binary join has been studied. There are indications of the existence of three calcium niobates. These compounds have been characterized by X-ray powder diffraction and optical data. Single crystal studies have given information concerning the crystallography of these materials.

The scanning speed of powder diffractometers can be increased by about two orders of magnitude by replacing the normal detection system (receiving slit/scintillation counter) by a linear position sensitive detector (PSD) which collects diffracted x-rays of a larger part of the diffractometer measuring arc simultaneously. The velocity increase is proportional to the section of the arc 29 in which the diffracted x-rays are detected. With respect to the Bragg-Brentano focussing geometry, a range of several degrees (typically 5°) can be tolerated without affecting the resolution remarkably. Diffractograms over extended angular regions of 2θ are received by slewing the PSD continuously along the arc while the diffracted x-rays are accumulated with their accurate 2θ angle address on a digital base.

The method has been named the continuous position sensitive detection technique (CPSD). With this technique, diffraction patterns with similar quality (resolution, linearity, peak/background ratio) as conventional, scintillation counter recorded diagrams can be received at slewing rates of several hundred degrees per minute. Additionally, the CPSD technique augments the number of crystallites contributing to the diffraction intensity by the same amount, thus producing much better crystallite statistics for quantitative measurements.

Dental amalgam has been used as a filling material in dentistry for over 100 years. The reactants, Ag3Sn alloy and mercury, form silver-mercury and tin-mercury products. Previous X-ray diffraction studies have resulted in some disagreement concerning unit-cell structure and parameters of the products. In this study, X-ray diffraction measurements were carried out on tin-mercury mixtures, tin-mercury alloys, dental amalgam, and single crystals of tin and mercury. The diffraction data for the tin-mercury alloys were programed for an IBM 650 computer utilizing Cohen's least-squares method. The tin-mercury product was found to be a solid solution possessing hexagonal-symmetry elements. The parameters ranged from: c0 = 2.995 A to 2.984 A, co/ao = 0.931.

A relationship is derived between X-ray intensity and particle size for a minor constituent in a powder sample. Theoretical and experimental curves are compared for several elements which are of importance in mining applications. Based upon these curves, some general guides are established relating to a method of predicting the particle size required for a given application. It is also shown that the relative intensity of a minor constituent is independent of the absorption coefficient of the matrix, if the particle size of the matrix is constant. Mineralogical effects, which relate to the occurrence of an element in two or more forms of chemical combination, are discussed and several examples in mining applications are cited.

The state of the art of stress evaluation on materials having non-linear lattice strain distributions is presented.

New results on heterogeneous materials with measurements conducted on both phases of the material show compensation of the shear stress components σ13 in ground surface layers of (α+β) brass. There is only the compensation of normal components σ11 of (α+γ) steel after plastic straining.

The fundamental aspects and the evaluation of macro- and microresidual stresses on materials having preferred orientation are broadened. The use of Mo-Ka-radiation shows linear lattice strain distributions, as a result of minimizing the influence of micro residual stresses causing oscillations. The interplanar distance- or strain-polefigure shows similarities with the intensity polefigure.

The knowledge of the theoretical influence of stress distribution with depth from the surface of the material is extended. The experimental procedure should use either different radiations having different penetration depths or a low-penetrating radiation in combination with removal of surface layers.

A scanning range over Bragg angles from −163 to +163° 2θ is obtained by combining a diffractometer capable of scanning both sides of the primary X-ray beam with a very short (3-in.) high-power focused X-ray tube. The ability to scan the included angle 4θ between respective diffraction profiles on either side of the primary beam over the entire range of Bragg angles, provides a direct method of eliminating errors caused by a displacement of the specimen surface from the axis of the goniometer. The method is demonstrated by determining the lattice parameters of standard specimens used in the I.U.Cr. Precision Lattice Parameter Project.

X-ray diffraction observation of the material internal structure beneath fracture surfaces provide fracture analysists with useful information to investigate the conditions and mechanisms of fracture. X-ray fractography is a generic name given to this technique. In the present study, the residual stress on the fracture surface of the compact tension specimens for toughness tests was measured by X-ray diffraction. The effects of notch-tip radius and tempering temperature on the fracture toughness are discussed based on the results of X-ray fractography and fracture micromechanisms.