The coming era of reduced defense funding will dramatically alter the way in which advanced materials develop. In the absence of large funding researchers must concentrate on reducing the time that the R&D of a new materia) consumes. One way in which speed may be achieved is via the development of very fast dynamic characterization procedures which can rapidly and intelligently monitor and optimize the formation of a desired microstructure. Another potential advantage to this approach is its ability to characterize the actual amount of material which goes into a final product; permitting a rapid transition from R&D to manufacturing by avoiding the problems associated with scale-up. Example high-temperature dynamic characterization procedures have been applied to the problem of trying to improve the current carrying capacity of the YBa2Cu3O7-8 ceramic superconductor by melt-texturing. These procedures have led to a technique for the preparation of specimens with Jc on the order of 10,000 A/cm2.

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.

We report the development of a novel, pulsed x-ray diffraction system with picosecond time resolution. The system has been used to study the heat transport in gold, platinum and silicon crystals heated by 10 ps, 193 nm laser pulses. Further developments and applications of time resolved picosecond x-ray diffraction are discussed.

The aim of this article is to provide an overview of the applications of neutron powder diffraction in materials science. The technique is described with particular attention to comparison with the X-ray powder diffraction technique to which it is complementary. In this context, emphasis is placed on rapid data acquisition and in-situ studies of phase transitions. Examples of some applications of the technique to materials science problems, at the HIFAR research reactor, Lucas Heights are included.

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.

The accuracy of Quantitative Rietveid Analysis (QRA) was examined in terms of the plausibility of the set of refined parameters as well as the realization of the expected quantitative result. This route was pursued due to the two mutually exclusive characteristics that a powder exhibiting the calculated (ideal) diffraction intensity would possess; it would have infinitesimal domains to alleviate the effects of extinction but at the same time infinitesimal surface area to eliminate the volume of the disordered surface or amorphous phase. The specimens were mixtures of NIST Standard Reference Material (SRM) 640b, a silicon powder with a mean particle size of 7 pin (certified with respect to lattice parameters), and SRM 676, an alumina powder with a submicrometer crystallite size (certified for quantitative analysis). Good agreement between the particle size of SRM 640b, determined by laser scattering measurements, and its domain size, determined by using the Sabine model for extinction, were obtained with the use of improved background functions in refinements of neutron time-of-flight (TOF) powder diffraction data. These data, in conjunction with the plausibility of other refined parameters such as temperature factors, led to a credible measurement of the amorphous content of SRM 676 and a verification that TOF data can yield unbiased quantitative results. A new SRM for quantitative analysis of silicon nitride was certified with respect to the a, p and amorphous (impurity) phase content with the use of TOF diffraction and SRM 676 as the reference phase. Results from XRD data were found to be less sensitive to background function, though improvements in the Rietveid analysis of XRD data were achieved.

A new procedure for the quantitative phase analysis using the whole–powder–pattern decomposition method has been proposed (Toraya and Tsusaka, 1995). The procedure is based on the determination of the scale factor for the profile intensity of each phase in a mixture, which is identical to the ratio of integrated intensity in a mixture to that of the corresponding reflection in a single component sample. Weight fractious were obtained by solving the simultaneous equations, of which coefficients include the scale factors and the mass absorption coefficients. In a previous study, the mass absorption coefficients were calculated from chemical compositions and u,/p data of respective phases. In the present study, an alternative way of deriving the weight fraction without using the knowledge of chemical composition is proposed.

In this investigation we have examined how the full width at half maximum intensity (FWHM) and asymmetry of x-ray powder diffraction line profiles are influenced by the instrumental conditions adopted. Experimental x-ray data has been collected for a matrix of instrumental conditions by systematically varying the divergence slit angle (and the corresponding anti-scatter slit) over the range 0.25° to 1.25°, by using either a 0.05mm or 0.2mm receiving slit, or by removing the diffracted beam Soller slit. The line profile Standard Reference Material, SRM, 660 (LaB6) was used as the powder specimen in that it imparts minimal specimen induced broadening to the diffraction profiles. X-ray data were collected on a conventional, divergent beam, x-ray diffractometer using CuKα radiation.

The FWHM of the CuKα1 component can be as low as 0.035°2θ for high resolution conditions, but is normally ∼0.1°2θ at 2θ ≈ 30° for the instrumental conditions adopted in routine diffractometry. Below 2θ = 50°, the divergence slit has a significant effect on the FWHM and is the major cause of the increase in FWHM with decreasing 2θ. Results are presented of the 2θ dependence of FWHM values for each of the instrumental conditions recorded. A general relationship for the 2θ dependence of the FWHM and the asymmetry has been investigated to supersede the inappropriate Cagliotti expression frequently used in x-ray Rietvcld refinement.

In smectite analyses, the investigation of the attenuation contribution to quantitative x-ray diffraction (XRD) analysis is a most important topic, including Fe content and distribution. This is the first part of a comprehensive study on smectite analysis addressing the nature and location of Fe atoms within the octahedral sites, interlayer regions, and intergranular interfaces. This first paper treats the mass attenuation measurements and calculations (Davis and Johnson, 1987). Additional reports will be made in the future on Fe studies involving measured and calculated reference intensity ratio measurements and structural studies based on SEM and TEM analysis.

Determination of the species of compounds present in ambient aerosols has received increasing interest in recent years (Harrison and Pio, 1983; Davis, 1984; Davis and Maughan, 1984; Harrison and Sturges, 1984; Sturges et al, 1989; Possanzini et al, 1992; Havliek et al., 1993), but the U.S. Environmental Protection Agency's conversion to the PM10 standard in 1987 has made quantitative analysis of fine particle aerosols more difficult because of the much smaller deposited mass on these filters, as well as the increased proportion of carbon-bearing material naturally present in the smaller diameter portion of the atmospheric aerosol size distribution. Under the old TSP (Total Suspended Particulate) collection protocol, filter loads of 400-2000 μg cm-2 of 10-20 μm mean diameter particles, corresponding to 24-hour collections at ambient concentrations of 100 to 500 μg m-3 at 40 CFM flow rates, resulted in excellent diffraction patterns scanned directly from filter segments.

As a result of interest in the characterization of materials with large d-spacings and layer periodicities, it has become necessary to develop a low-angle diffraction material which has welldefined diffraction peaks down to very small 2θ angles. The use of silver behenate, CH3(CH2)20COO-Ag, was introduced by one of the authors (TB) at the 1991 International Centre for Diffraction Data (ICDD) Annual Meeting and was shown to have a set of well-defined (001) diffraction peaks down to 1.5° 2θ when using CuKα radiation. The silver behenate diffraction peaks were observed to be slightly asymmetric with relatively long tails at the low angle side of the peaks. The average crystallite size along the c-axis was estimated using the Scherrer equation and was found to be 900 Å.

A task group of the JCPDS-ICJDD Data Collection and Analysis Subcommittee was established with the charge of investigating the use of silver behenate as a possible low-angle calibration material for diffraction applications. Utilizing several data collection and data analysis techniques, d001 long-period spacings in the range of 58.219-58.480 Å were obtained. Using the same collected data and one data analysis refinement calculation method resulted in long-period spacing with a range of 58.303-58.425 Å. Data collected using a silicon internal standard and the same singular data analysis calculation method provided d001 values with a range of 58.363-58.381 Å.

The formation of a full-range 2θ diffraction sample was also investigated. Silver behenate and inorganic powders were mixed with an epoxy binder to form a permanent sample which provides diffraction peaks over the entire 2θ range of a powder diffractometer.

The majority of sulfide mineral patterns in the International Centre for Diffraction Data Mineral Powder Diffraction File have historically been of low quality (e.g., FN < 10 and qualitative intensities). A five-year study has resulted in upgrading approximately 20% of the poorer quality patterns and will triple the number of “star quality” patterns. This paper describes the experimental methods used to obtain these upgraded patterns. The essential role of diffraction pattern calculations and diffractogram simulations is stressed.

A file of digitized diffraction traces for clay minerals has been developed as a test for the usefulness of such traces in the analysis of clays and clay deposits. The kaolin, smectite, mica clay and chlorite groups are represented by patterns of the most common mineral species in the small crystallite size which is typical of their natural occurrences. Patterns are included for the oriented sample and for glycolated and heated samples when appropriate. This database may form a nucleus for an extensive collection of clay mineral traces in the same manner as the early Powder Diffraction File did for the modern PDE.

The measurement of the total electron yield (TEY) emitted from a solid specimen when irradiated by monochromatic x-rays is used for quantitative information on the specimen. For this purpose one has to determine the increase of TEY in the course of a variation of the photon energy from below to above the absorption edges of the specimen elements. These increases are the analytical quantities and are correlated with the composition of the specimen. The detected electrons are photo, Auger and secondary electrons. Most of them lost some of their original kinetic energy due to inelastic collisions along their path from the atom of origin to the surface. Low energy electrons are especially found in the secondary electron peak with electron energies of less than 20eV. Electrically nonconductive specimens under x-irradiation tend to positive surface charging.

The X-ray reflectivity technique was used to study the annealing effect on layer structure of Ta/FeMn/NiFe/Cu/NiFe/Ta multilayer thin films on Si substrates. High-resolution specular reflectivity data were collected and analyzed by least-squares refinement. Results on layer thickness, density and roughness were obtained and correlated with the magnetic properties of the films.

Results on least-squares refinement of X-ray reflectivity data obtained with a conventional powder diffractometer are reported. A model containing an oxygen contaminated surface on Pt was used to refine experimental data for a “500-Å” Pt film on Si. Values of layer thickness, density, and roughness determined by least-squares refinement agree with those obtained from highresolution reflectivity data. The results were found to be insensitive to the film-surface alignment. An agreement of ±2.3 Å for Pt thickness, 8% for density, and 2.5 Å for roughness was obtained when the surface was aligned to within the divergence of the incident X-ray beam. The least-squares refinement method was also used to analyze two sputtered “300-Å” Pt films deposited at 4 and 20 × 10-6 Torr Ar pressure. Results showed a significant increase in Pt thickness and a decrease in density for the 20 × 10-6 film probably caused by a large amount of Ar trapped in the film.