The development of preferred orientation, by powder compaction was studied in several single phase, two-phase and three-phase powders. It was found that texture formation depends strongly on the properties of the powder particles and the preparation technique. In powder mixtures strong interaction effects were observed which either enhanced or reduced the degree of the preferred orientation. The required degree of series expansion of the texture function ranged from zero up to about fourteen.

Polycrystalline and powder diffraction is the most commonly practised method of x-ray analysis. During the last decade the construction of dedicated synchrotron radiation sources has resulted in the renaissance of these x-ray analysis methods; ab initio structure analysis and refinement, quantitative analysis of the structure, composition and stress in thin films and on surfaces, have all been improved. New techniques providing extremely high resolution, using anomalous dispersion, diffraction and scattering at grazing incidence to control x-ray penetration depth, have been developed. This brief review of work with W. Parrish at Stanford Synchrotron Radiation Laboratory and R. J. Cernik at the Daresbury Synchrotron Radiation Source is extended to indicate how third generation sources might be exploited in materials science.

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.

Improvements in sample preparation methods have resulted in increased accuracy in x-ray powder diffraction intensity measurements. This improvement has focused scrutiny on the instrument as a potential source of error. NIST Standard Reference Material, SRM, 1976 consists of a sintered α alumina, corundum, plate certified with respect to 12 relative intensity values from 25 to 145 degrees 2θ. Its function is to allow for standardization of powder diffraction intensity as a function of 2θ angle (instrument sensitivity). An increase in the accuracy of interlaboratory comparisons of diffraction intensity and related determinations will result. Utilization of the SRM requires the user to collect intensity data from the test instrument in a manner which conforms to that used in the certification. Graphical interpretation of the ratio of these data to those on the certificate will allow for appropriate judgment as to the condition of the test instrument. Discontinuities in the data indicate a malfunctioning or misaligned instrument. Systematic bias, introduced by design characteristics of the test instrument, manifests itself in terms of a pattern in the data other than a horizontal straight line with value of one. This bias may be removed with the calculation and application of a correction curve.

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.

Silicon powder, available as a Standard Reference Material, fulfills most of the requirements for a two theta standard. However, It has no diffraction lines at the low 2θ values characteristic of some species. Standard synthetic mica is available but expensive.

Experiments with a commercially available high silica zeolite have shown that it is a valuable secondary standard. It is non-toxic, stable, inexpensive and possesses a large (24 Å) unit cell. Peaks show clearly from 14 Å (6°2θ for Cu Kα).

An example is given of the use of this secondary standard in determining lattice parameters.

Trace analysis of quartz at the <0.1 wt% level can be routinely accomplished by x-ray diffraction using rotating pressed-powder briquettes and a peak deconvolution strategy due to Wiedemann, et al. (1937a, b) which permits reproducible determination of background and enhances peak resolution without changing the integrated intensity.

Four calibration methods were tested: (1) calibration with perlites microscopically analyzed by Hamilton and Peletls (1988), (2) with artificial mixtures of quartz and glass, (3) with chemical analysis and massbalance calculation of quartz in glass mixtures, and (4) with a new method of additions for XRD.

Methods (2) and (4) gave the best results. Method (2) has a precision of 16.9 pet at the 0.1 wt% level and a LLD of 0.05 wt% at 3σ. Method (4) is particularly attractive because large spikes can be used which minimize homogenization errors and permit preparation of standards which have properties very similar to run-of-the-mill samples; the problem of non-zero intercepts is avoided.

Recently some of the above authors determined the structure of an unsolved organic compound employing X-rays from a Synchrotron, an Imaging Plate, and a large radius camera. It would be more desirable if the high quality powder diffaction data could be obtained by a diffractometer or a camera of laboratory use. Therefore a multimode X-ray powder diffractometer which can be used for various experimental geometries such as Bragg-Brentano mode, Guinier mode and parallel beam mode was constructed in order to find the highest resolution geometry. In this paper wc present the results of the measurements employing these three modes.

The Bragg-Brentano focussing method (2θ/θ scan) is widely used in X-ray powder diffractometers. We have recently manufactured a diffractometer (2θ/α scan) whose incidence and reflection sides are asymmetrical. This report describes the optical system, including evaluation and application. The present method enables the following benefits to be obtained by simply changing the sample-to-receiving slit distance b without changing the X-ray source-to-sample distance a: (1) enhanced angular resolution, (2) increased diffracted X-ray intensity, and (3) variable asymmetrical angle. The experimental results show that the focussing condition of this optical system was satisfied. It also shows that the intensity of diffracted X-rays could be increased by approximately 1.4 times at b = 100 mm when the intensity at a = 185 mm and b = 185 mm was assumed to be 1. Furthermore, it was verified that FWHM can be reduced by making sample to receiving slit distance greater.

A two-crystal spectrometer for chemical state analysis by high-resolution x-ray fluorescence spectrometry employs hall-screw and slide mechanisms rather than gears to obtain a 2θ scanning range of 40° -147°; a Δ2θ scanning step of 10−4 deg under vacuus; a 2θ resolution of 10−4 deg in determination of an intercrystal angle with encoder-based measurement; and servomechanical control of position. The spectrometer, although simple in structure, is a powerful instrument for chemical state analysis, as demonstrated by its high resolution, precision, and stability; as demonstrated in the determination of the Kα1 lines of first transition metals with Si(220) as analyzer crystal, and in its application to a systematic study of the chemical effects on Ni Kα1 and Kα2.

The design, construction and operation of toroidal focusing X-ray monochromators have been described in detail by Marcus, et al. (1980) and by Furnas, et al. (1982), Marcus, et al. used 100 mechanically damaged, singly bent LiF (200) (2d = 4.02 Å) single crystals in a toroidal array to focus Cu Kα characteristic X-rays (8.04 keV, 1.54 Å, Θ = 22.6 deg). The diameter of the LiF toroid was 166 mm and the source-detector distance was 400 mm. Furnas, et al. used a series of singly bent, highly oriented graphite (2d = 6.72 Å) crystals, also in a toroidal array, to focus Pb Lα, Se Kα, Th Lα and U Lα X-rays (10.5 - 13.6 keV, 1.18 - 0.91 Å, Θ= 10.1 - 7.8 deg). Their system dimensions were not disclosed. The LiF and graphite crystals were both curved along the direction of X-ray propagation. That is, the cylindrical axes were orthogonal to the X-ray path.

The Fuji Imaging Plate (IP) is a 2-dimensional detector in which a latent X-ray image is stored as a distribution of color centers on a photostimulable phosphor (BaFBr:Eu2+) screen. It has a large effective area, wide dynamic range and high sensitivity. Thus it has been widely used not only in medical but also in scientific and industrial fields. Particularly in X-ray structure analysis, mainly of proteins, it has been used extensively and achieved good results.

On the other hand, few applications have been reported in the field except for structure analysis, in spite of the superior performance of the IP which will give significant advantages in various measurements which have been done using an X-ray film such as electric device and fiber specimen.

Therefore we report here the basic performance of R-AXIS II(Rigaku Automated X-Ray Imaging System II), an IP reader made by Rigaku, and some applications of X-ray diffraction measurements using IP.

For time-resolved diffraction studies under high temperature and/or high pressure, we designed a new diffractometer incorporating a curved position sensitive detector and tested the rapid intensity measurement and the resolution of the angular dispersive diffraction. The diffraction profiles were compared with those from energy dispersive diffraction. Rapid intensity collection has been carried out with a CAMAC module. A curved position sensitive detector with a 120° working angular region was installed on the off-centered four circle diffractometer. Only a few seconds were needed to obtain a whole powder diffraction because of the extremely high counting efficiency due to the streamer mode.

Time-resolved observations of the dehydration reactions of Mg(OH)2 and Ca(OH)2, have been undertaken by angular dispersive and energy dispersive x-ray powder diffraction at high temperature. The in situ observations of the dehydration process provide kinetic information, such as the reaction rate, the apparent activation energy and the dehydration mechanism.

In-situ, high temperature X-ray diffraction (XRD) is an extremely useful tool for studying, monitoring or investigating crystal structure modifications as well as phase transformations in crystalline material during thermal treatments in controlled atmospheres. This technique has been used to investigate the thermal behavior of materials such as carbonate minerals, ceramic fibers, coating pigments, etc. The advantages of such a technique over the conventional practice, where samples are heat treated in a separate oven and then analyzed by XRD include: consistency of sample placement; preservation of high temperature structures to facilitate observation of metastable phases that are unstable upon exposure to outside atmosphere or during cooling; real time monitoring of reactions that occur, and products that are formed at a desired temperature or environment; and need for multiple samples or analysis.

A procedure for the accurate determination of unit-cell parameters using conventional Xray powder diffractometry is described. Two important factors in the procedure are: 1) the use of high-resolution-type diffractometer, which can suppress the axial beam divergence and thus gives nearly symmetric diffraction profiles in the low 2θ region and 2) the use of a new algorithm for systematic peak shift correction during the least-squares determination of unit-cell parameters of a sample with an internal standard [Toraya & Kitamura (1990). J. Appl. Cryst. 23 , 282-285]. The procedure has been tested by measuring successively the unit-cell parameter of W, CeO2, and Si in three mixtures, Si+W, W+CeO2, and CeO2+Si: the unit-cell parameter of W, which was first determined by using NIST SRM 640b Si powder as an internal standard reference material, was used as a standard reference value to determine the unit-cell parameter of CeO; in the next W+CeO2 mixture, and so on. The difference between the end value of observed Si unit-cell parameters and the starting value of 5.430940(35) Å were just 1 to 5 p.p.m. High accuracy is attainable in measuring the uni-cell parameters even with the conventional powder diffractometry provided with the nearly symmetric diffraction profile and the algorithm for peak shift correction used in the present study.

The basic diffraction techniques for examining the stress tensor are reviewed, with particular emphasis on what can be done without knowing the unstressed lattice parameter(s). Examples are given of the residual stresses in thin films, how to measure the bonding and yield stress in composites and separating the micro and macrostresses to examine load sharing between phases.

Starting in Germany (Garmisch Partenkirchen, 1986) we had the 1st ICRS (Int. Conf. on Residual Stresses). The second was held in France (Nancy, 1988), the third in Japan (Tokushima 1991). In all areas, the diffraction measurements furnish exceptional contributions, and in many cases they are the only methods capable of solving problems. Because of the importance of the diffraction methods, the literature on residualstress analysis (RSA) has enlarged in the last years, Figure 1.

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.

Intergranular residual stresses can exist in zirconium alloys, especially when there is a large distribution of grain orientations. The stresses result from the anisotropic plasticity and thermal expansion of the hexagonal close-packed crystal structure of α-zirconium. Apart from complicating the characterisation of materials using lattice parameter measurements, the intergranular stresses can significantly affect material behaviour, especially in nuclear reactor environments, and there is therefore a great deal of interest in their measurement.

The effects of specimen preparation and surface relaxation on X-ray diffraction measurements of lattice parameters of zirconium alloys have been investigated by comparing bulk neutron diffraction with X-ray diffraction on identical materials. The results show that: (i) intergranular or interphase residual stresses exist in dual-phase Zr-2.5Nb pressure tubes; (ii) the stresses normal to the surface of an X-ray diffraction specimen are not relieved completely when there are intergranular residual stresses in the material. One can conclude that intergranular stresses have to be considered when determining chemical compositions from lattice parameter measurements and also when measuring macroscopic residual stress using X-ray diffraction.

A self-consistent scheme is proposed for the evaluation of stressfields which vary strongly within the penetration depth of the X-rays in polycrystalline specimens which are elastically isotropic and homogeneous on a macroscopic scale. Very precise diffraction experiments have to be performed for practical applications.