EDXRF analysis is conveniently split into two parts: (1) the determination of X-ray intensities and (2) the determination of elemental amounts from X-ray intensities. For the first, most EDXRF analysis has been done by some method of integrating the essentially Gaussian distribution of observed full energy pulse heights. This might be done, for example, by least-square fitting of Gaussian distributions superimposed on a straight line or a quadratic background. Recently more elaborate shapes of the energy peaks also have been considered (Kennedy, 1990). After the X-ray intensities have been determined, interelement effects between the analyte element and other elements must be corrected for in order to obtain the elemental amounts from X-ray intensities. This correction can be done either by an empirical correction procedure as in the influence coefficient method which requires measurements on a number of standard samples to determine the required coefficients, or by theoretical calculation as in the fundamental parameters method which does not require standard samples.

This study presents a unique and novel enhancement of the double crystal diffractometer which allows topographic mapping of X-ray diffraction rocking curve half widths at about 100-150μm spatial resolution. This technique can be very effectively utilized to map micro-lattice strain fields in crystalline materials. The current focus will be on the application of a recently developed digital implementation for the rapid characterization of defect structure and distribution in various semiconductor materials.

Digital Automated Rocking Curve (DARC) topography has been successfully applied for characterizing defect structure in materials such as: GaAs, Si, AlGaAs, HgMnTe, HgCdTe, CdTe, Al, Inconnel, Steels, BaF2 PbS, PbSe, etc. The non-intrusive (non- contact & non-destructive) nature of the DARC technique allows its use in studing several phenomena such as corrosion fatigue, recrystallization, grain growth, etc., in situ. DARC topography has been used for isolating regions of non-uniform dislocation density on various materials. It is envisioned that this highly sophisticated, yet simple to operate, system will improve semiconductor-device yield significantly.

The high strain sensitivity of the technique results from combination of the highly monochromated and collimated X-ray probe beani, the State of the art linear position-sensitive detector (LPSD) and the high-precision specimen goniometer.

The aluminum K X-ray emission lines and bands from a series of aluminum binary alloys and other binary compounds were investigated using 6 kV electron excitation and a flat crystal vacuum spectrometer. The overall shape of the emission band and its energy position as a function of alloy composition was determined. It appears from the data that the aluminum K band undergoes changes in shape and energy position which are dependent on the electronic configuration of the element with which the aluminum is chemically bonded. These band changes can be interpreted as indicating a change in the bonding character between the metal atoms. In the Al-Ni system, for instance, the Al K band becomes more symmetrical and shifts to lower energy as the nickel content is increased, indicating that perhaps the bonding on the aluminum atoms is becoming less metallic and more covalent in nature as the nickel to aluminum ratio is increased.

The aluminum Kα4/Kα3 satellite line intensity ratio also varies in an orderly manner in aluminum binary compounds. In general, these satellite line changes go hand-in-hand with the K band changes. If the K band shifts to lower energy, the Kα4/Kα3 intensity ratio will always increase in value.

Energy-dispersive X-ray fluorescence might advantageously be used for the determination of trace metals in water. Suspended material can straightforwardly be collected on a 0.45 μm pore-size Nuclepore membrane by filtration. Dissolved ion analysis usually requires a physical or chemical enrichment step. Spotting a 1.5 ml water sample on a Whatman-41 filter within a 29 mm diameter hydrophobic ring and drying by a cold air stream from underneath yielded a 50 ppb sensitivity for many elements, and a 18% accuracy. Filtration of a 200 ml water sample at the natural pH through a pair of Chelest-100 chelating ion-exchange resin loaded filter papers allowed 1-5 ppb sensitivities but suffered from the combination of limited load capacity and significant uptake of usually abundant alkali earth metals.

The two-angle and Sin2ψ methods of x-ray diffraction, residual stress measurement have been shown to yield anomalous results When applied to samples which have been plastically deformed uniaxially in tension or by rolling. These anomalous stresses, which are not true mechanical macrostresses, have been shown to arise from a nonlinear dependence,of d, the interplanar spacing employed for stress measurement, upon Sin2 ψ. A new method of x-ray diffraction stress measurement has been developed by Marion and Cohen which aLlows the separation of the Linear and nonlinear components of the dependence of d upon Sin2 ψ.

The two-angle and the Marion-Cohen x-ray diffraction methods are applied to the measurement of residual stresses in the machined and shot peened surfaces of steel and aluminum samples. The results indicate that machining deformation results in a nearly linear dependence of d upon Sin2ψ , and onLy a slight deformation texture. The two x-ray methods yield stress values in ground, turned, and shot peened steel and aluminum samples which agree within the estimated experimental error. Previous results are sighted showing agreement between the two-angle method and a mechanical stress measurement technique. The results indicate that, at least in steels, the multiaxial plastic deformation produced by machining does not significantly effect the accuracy of the two-angle x-ray diffraction stress mea surement method.

Pyroaurite and sjogrenite belong to the group of sandwiched lamellar metal hydroxides which have a fixed metallic ions MII:MIII ratio for a particular class. Their crystal structure consists of positively charged metal hydroxide blocks intercalated with negatively charged interlayers. The atomic positions for the interlayer are definite for a particular class. The exact chemical formula of the pyroaurite class is determined from crystal structure analysis to be MII6MIII2(OH)16-CO3-4.5H2O; it crystallizes in the space group Rm with a = 12.4376 Å and c = 23.4126 Å. Sjogrenite, MII6 MIII2(OH)16-CO3-4H2O crystallizes in the space group P63/mcm. The crystallogiraphy and structural relationship between these classes are discussed. Previous discussion on these compounds did not give any conclusion on the exact chemical formula and the atomic positions.

Chemical analysis of geological materials such as nickel ores has been accomplished by atomic absorption (1,3) x-ray fluorescence (11,14) and conventional wet methods (10). Procedures utilizing these techniques are capable of producing excellent results but are often difficult and time consuming.

Minerals often present serious problems in chemical analysis by wet methods. X-ray analysis can therefore offer the analyst considerable savings in time providing the obstacles which exist are understood and minimized or eliminated. The most serious problems to solve are absorption and enhancement effects, mineralogical differences among samples, sample preparation, and particle size effects which often influence the intensities of the analytical lines. In addition, the element of interest may be of low concentration in a variable and unknown matrix.

A programme of grazing incidence grating studies is described, undertaken in collaboraion with A.W.R.S. Aldermaston, U.K.A.E.A. Culham and N.P.L. Teddington. The wavelength range of interest is from lǺ - 300Ǻ with special emhasis placed on focusing systems for use below 5Ǻ.

Numerous studies have been conducted into the microstructural origin of the instability and unpredictability of various energetic materials. Some of these materials are RDX/HMX, Ammonium Perchlorate, Aluminum, etc. Many techniques both destructive and non-destructive have so far been utilized in an attempt to quatify the energetic properties of their composites. These composites may contain one or more energetic constituents in an elastomeric binder. Non-destructive X-ray characterization techniques have been successfully employed to measure several microstructural parameters. Previous studies have shown considerable differences among various production grade RDX. These studies reveal marked differences in the amounts of residual elastic strain and the distribution of dislocations (residual plastic strain) in the constituent RDX phase.

The focus of this study is to develop a technique for quantitative constituent phase analysis of solid-propellant (fuel) composites using conventional diffractometry. The use of a Curved Position Sensitive Detector (CPSD) greatly enhances the technique and allows real time applications in production environments. Through the use of computer based Systems and "user friendly" software the required Operator, skill and training have been considerably reduced. The CPSD System has been successfully used to quantify constituent phases (peak heights) and the amounts of residual elastic strain (peak shifts) in these molecular crystal powder mixtures.

It is envisioned that rapid, automated, non-destructive X-ray characterization techniques will greatly facilitate production based propellant quality control. A thorough understanding of the relationship between the energetics and microstructural parameters can also he obtained.

Identification or recognition of an unknown is a problem encountered in areas as diverse as X-ray diffraction, signature and voice verification, fingerprint identification, and spectroscopy(mass), infared(IR), ultraviolat(UV), Auger). Features uniquely characteristic of the unknown, which are used in the identification process, are called the “pattern” of that unknown. In a typical identification, the one or more sub-patterns (components) making up the unknown pattern are identified by a search through a set of known (standard) patterns to yield potential matches. This searching and matching can be done sucessfully by hand, especially if the number of patterns in the file of standards is not too great. When the number of phases which consititute the unknown pattern becomes extremely large the use of computers becomes a practical necessity if the search is to be conducted in a reasonable time. A comparison of X-ray search-match approaches with each other and with search-match capabilities existing in other fields may lead to better X-ray phase identification techniques.

Basic processing steps utilized in the fabrication of planar silicon devices include (a) substrate preparation, (b) epitaxial deposition, (c) thermal gvowth of silicon dioxide over the entire silicon wafer surface, (d) device pattern formation by photoetching techniques, and (e) diffusion of n-type or p-type elements through the holes to produce localized regions of desired conductivity, A detailed study of the various diffraction phenomena associated with such structures is presented. X-ray topographs of planar transistors show distinct contrast features such as excess diffraction intensity along the silicon oxide/silicon boundary and/or excess diffraction intensity inside the device area. The diffraction phenomena are discussed in terms of reversible elastic deformations, frozen-in lattice deformations, strain fields and imperfections generated by the various processing steps. A technique is presented to measure the sign of the elastic deformations. The phenomenon of stressjumping across semiconductors interfaces is described, and finally the implications of stress-strain relations on junction performance are stated.

Measurements on the heat affected zone of a weldment are presented using a gas filled position sensitive detector and a normal diffractometer equipped with a scintillation detector and a solid state detector. The sample, a surface ground titanium alloy, provided a difficult application for the X-ray technique from which a test of the real usefulness of the position sensitive detector could be made. The diffraction profile from the Ti alloy is very broad and the fluorescence produces a high background. The fluorescence is easily rejected using a solid state detector; however, the time of analysis is very long. With the position sensitive detector, the combination of increased energy discrimination over the scintillation detector and the simultaneous measurement of many data points over the broad peak enabled the measurements to be made for the same accuracy in much shorter times than for either the solid state detector or the scintillation detector.

Crystals with a dislocation density low enough so that individual dislocations can be resolved by X-ray diffraction contrast techniques should be regarded as highly perfect crystals. A complete description of the diffraction process, therefore, requires the approach of the dynamical theory of X-ray diffraction. In the Berg-Barrett arrangement each point on the crystal surface integrates the incident X-ray intensity over the angular range received from the X-ray source. For most experimental arrangements this range is about 1/2 degree and corresponds, therefore, to integrating over the entire range of reflection of the crystal, which is of the order of a minute or so of arc. The Berg-Barrett image is a recording of a localized integrated intensity, integrated over the complete range of incident angles. We consider as essential, however, primarily the range of total reflection, since it makes the major contribution to the integrated intensity.

The dynamical theory shows that the details of the diffraction process depend very strikingly on the boundary ocnditions at the crystal surface through two angles of incidence - one between the incident beam and the crystal surface, the other between the incident beam and the diffracting plane of atoms. Calculations of the parameters of the dynamical theory which describe the diffraction process in the Berg-Barrett arrangement show that the description depends very strongly on the details of the specific boundary conditions employed. In particular, two parameters seem especially important in dislocation image formation: 1) ΔθR, the angular range of the exit beam diffracted from the crystal, which we call the range of total rejection to distinguish It from ΔθA, the angular range over which the entrance beam is totally accepted, and 2) σe, the extinction coefficient, the parameter which describes the X-ray penetration depth. Both parameters are extremely sensitive to the specific boundary conditions employed.

This dynamical theory approach suggests that, by suitable choice of the experimental conditions, the boundary conditions can be advantageously adjusted so that satisfactory Berg-Barrett images can be obtained.

The results of two crystal measurements of potassium acid phthalate crystal first order parallel position rocking curves, percent reflections, and reflection coefficients are presented. They cover the 4-24 Ǻ wavelength range and are typical of results with cleaved crystals illuminated over areas of one-half to two square inches. The energy resolution available with these crystals is shown to be nearly constant at about two-thirds of an electron volt over most of the energy range studied and the coefficient of reflection is also nearly constant at about 1 x 10-4 radians. A pronounced line-like reflectivity structure at 23.3 Ǻ is exhibited which is probably associated with oxygen atom K-shell absorption.

This paper summarizes developments in the field of high-temperature X-ray diffractometers through 1959, evaluates various furnace designs, and describes briefly the X-ray diffraction facilities of the Federal Bureau of Mines.

X-ray optics, for those furnaces that have precision sample movements, are equivalent in resolution and line profile to conventional X-ray techniques. There is a 10-25% loss of intensity due to absorption of X-rays in the furnace windows, magnitude of which depends on wavelength and type of window used, and a reduction (5–40° 2θ) of useful angular range from limiting X-ray windows, radiation shielding, or the viewport for an optical pyrometer. In oxidizing atmospheres, temperatures up to 1500°C were obtained with furnaces wound with platinum—20% rhodium wire. Under nonoxidizing conditions temperatures of 1800 to 2000°C were obtained with both tantalum-foil and tungsten-wire heaters.

Accurate temperature measurement over the area and depth of samples being studied is the most difficult problem in high-temperature X-ray diffractometry. Below 500°C, there are several furnace designs which are reported to reduce thermal differentials to less than 1°C across the sample. However, at temperatures around 1000°C, there are thermal gradients of 20-30°C/cm across the sample and 100–600°C/cm through the sample holder, making thermocouple location critical. Secondary standards have been used extensively to calibrate the furnaces; however, there is disagreement concerning which are the most reliable data to use. For these reasons, plus others discussed in this report, there is a probable error in the temperature determination of ±10 to 20°C at 1000°C, with the error increasing with temperature.

Solid solution decomposition of several aluminumrich aluminum-zinc-silver alloys were investigated using x-ray small angle scattering, x-ray diffraction (Guinier and Dewolff camera) and transmission electron microscopy. A decomposition sequence was observed directly fay means of hot stage electron microscopy, to be:

G.P. zones were observed to exist in all of the ternary Al-Zn-Ag alloys used in this investigation. Only one type of G.P. zone was detected and evidence is given which indicated that the G.P. zone formation was governed by the existence of a metastable miscibility gap. Experimental results also indicated that the lattice of the matrix is distorted by the presence of the G.P. zone.

A transition phase, designated ɛ', was observed to nucleate on defects in the matrix and to have a hexagonal close-packed structure. The ɛ' phase is partially coherent and much more regular in spatial distribution than the equilibrium ɛ phase.

Gas flow proportional counters for the detection of soft X-rays were introduced about ten years ago. These detectors offered the advantages of high sensitivity, good energy discrimination qualities and the ability to handle high counting rates. Since that time they have been used for ultra-soft and harder X-rays as well, both as detectors in standard spectrographic instruments and as energy discriminating instruments themselves in various so-called nondispersive applications. Depending upon the particular instrumental application, however, their use has led to considerable complication of the associated electronic circuitry in order to realize their advantages. For the most effective use of these counters (and of sealed proportional counters as well) it is necessary to have a clear understanding of the effect of various design parameters and operating conditions on their performance. The dependence of the shape of the pulse height distribution on the operating voltage, pressure and counting rate is described as a function of the energy of the radiation detected and the nature of the gas. Stability requirements on. counter tube high voltage supplies and operating pressure are discussed. Shifts of pulse height distributions toward smaller pulse sizes with increasing counting rate are described and the dependence of these shifts on the various parameters and on wavelength are discussed. Techniques for eliminating the shifts and the implications of these techniques for the associated electronics are described.

A position-sensitive proportional counter (PSPC) with high counting efficiency has been made for stress analysis with low intensity X-rays such as microbeam X-rays.

This PSPC system has made it possible to measure the residual stress in a small region such as a fatigue crack tip in very short time compared with the measurement by standard diffractometer or film methods.

Recent years were marked by a rapid increase of interest in the ase of x-ray fluorescence for on-site chemical characterization of contaminated soils and waste materials.

The known advantages of the XRF technique, such as capability of simultaneous, multielement analysis, speed of measurement (10 to 100 seconds), little or no sample preparation, wide concentration range, “portability,“ and ease of integration into environmental monitoring station(s), make it specifically suited for this application.

Major difficulties still inhibiting wider use of the XRF for hazardous waste screening stem from the lack of suitable calibration samples and proper protocols, as well as from the low awareness of the industry about the technique.

IARC's designation of crystalline silica as a “probable carcinogen” triggered the requirement to label products containing greater than 0.1 % crystalline silica. For perlite and other materials which may contain crystalline silica in levels close to 0.1% an accurate determination is critical from both legal and marketing considerations.

Existing analytical techniques for the determination of crystalline silica at levels of less than 1.0% were found to be inadequate to meet the new requirements. An improved technique based on x-ray diffraction has been developed specifically to analyze perlite for crystalline silica, which occurs largely in the form of quartz, at the 0.1%. level. The technique employs long counting times and improved sample preparation and mounting to increase both precision and accuracy, and to lower the detection limit to less than 0.1%.

The technique was tested on a large number of samples from a variety of sources and proven to give excellent results for all types of expanded perlites and perlite ores. The procedures developed are applicable to a wide variety of materials in addition to perlite.