Two different inversion methods, the inverse Laplace method and the linear constrained numerical method, for retrieving the z-profiles of diffraction data from experimentally obtained τ-profiles were compared using tests with a known function as the original z-profile. Two different real data situations were simulated to determine the effects of specimen thickness and missing τ-profiles data at small τ-values on the retrieved z-profiles. The results indicate that although both methods are able to retrieve the z-profiles in the bulk specimens satisfactorily, the numerical method can be used for thin film samples as well. Missing τ-profile data at small τ values causes error in the retrieved z-profiles with both methods, particularly when the trend of the τ-profile at small τ is significantly changed because of the missing data

Intermediate aluminum oxides (aluminas) have broad X-ray diffraction (XRD) peaks. Many of the phases have similar XRD patterns with overlapping of major peaks. To characterize a multi-component alumina mixture several regions of multiple overlapping peaks are examined. Each region is integrated to a single sum without regard for individual peaks. The integrated regions are applied to various ratio functions obtained from single component standards. By using an iterative technique, the functions converge to yield weight fractions for up to six alumina phases.

Techniques for the computer-assisted evaluation of crystallographic data have been developed to improve the data compilations of the NBS Crystal Data Center and the JCPDS—International Centre for Diffraction Data. The resulting computer program, NBS*ATDS80, can be used for the analysis of unit-cell and powder data by the general scientific community as well. NBS*AIDS80 is written in FORTRAN to permit implementation on a wide variety of computers, and input may be from cards or from a terminal. The research and analysis components that will be of use to the individual scientist include the following:

• 1) Calculation of the Crystal Data cell, determinative ratios, and space group for the comparison and reporting of unit cell parameters in a standard setting and for the identification of unknowns.

• 2) Determination of the reduced cell, reduced form number, and the unit cell with the highest metric symmetry.

• 3) Calculation of the molecular weight from the formula using the most recent atomic weights, and comparison of the density calculated by the program with the measured density.

• 4) Generation of d-spacings and indices for any input cell and crystal system.

• 5) Comparison of input powder data with calculated d-spacings, indexing of lines based on known unit cell parameters, and calculation of figures of merit.

This paper reports and discusses the results of a computer modeling study on powder diffraction profile analysis for crystallite size and strain of polycrystalline materials. The results of this computer modeling show that if the spans of diffraction profiles in reciprocal space (1/d) are not carefully chosen, an overestimation on size and an underestimation on strain may result in analysis by both the Warren-Averbach and the Hall-Williamson methods. A general way to eliminate such errors based on profile fitting and regeneration is presented and discussed in this paper.

A precise method for detenaining unit cell dimensions of semiconductor single crystals has been developed. An accuracy of ± 0.00002 Å and a precision of ± 0.00001 Å is achieved.

The method is used to determine variations in the cell parameter of GaAs as a function of surface defects, homogeneity across and along an ingot, evaluation of epitaxial layers, effects of heat treatments and structure defects induced by oxide diffusion masks on a substrate. The application of the technique to GaAsP alloys permit accurate and rapid study of sample composition and homogeneity.

Computed tomography (CT), commonly known as CAT scanning (computerized axial tomography), is a technology that produces an image of the internaI structure of a cross sectional slice through an object via the reconstruction of a matrix of X-ray attenuation coefficients. This non-destructive method is fast (50 ms to 7 min per image depending on the technological generation of the instrument) and requires minimal sample preparation. Images are generated from digital computations, and instruments essentially have a linear response. This allows quantitative estimations of density variations, dimensions and areas directly from console displays.

The back reflection x-ray divergent beam technique is examined as a tool for studying elastic strains. In particular, a method of calculating interplanar spacings using a least squares fit of experimental "conic" coordinates to Newman's general equation for back reflection (J. Appl. Cryst. 3 (1970) 191) is described. Using this technique, interplanar spacings can be obtained from partial conies. To determine the precision of this method an unstrained silicon single crystal is studied, and the errors associated with determining its interplanar spacings are discussed. The technique is then applied to elastically strained silicon and the results compared to theoretical predictions. It is shown that strains down to 2 × 10−5 are readily measured on high angle planes in silicon.

The Powder Diffraction File (PDF), published by the JCPDS-International Centre for Diffraction Data, is one of the most widely used scientific data bases. It currently consists of about 40,000 x-ray diffraction patterns, organized into 32 sets and 5 subfiles: metals and alloys, minerals, common phases, forensic patterns, and those from the National Bureau of Standards (NBS), New patterns are being added to the PDF at a rate of 2,000 patterns per year. The sources of these patterns are the literature, private contributions, grants in-aid projects, and the JCPDS Associateship at the NBS.

EPA's Air and Energy Engineering Research Laboratory is currently investigating the injection of dry calcium hydroxide [Ca(OH)2] into coal fired electric power plant burners for Che control of sulfur dioxide (S02) emissions.

When an x-ray diffraction profile Is measured for stress analysis or profile analysis by the use of a linear (straight line) position sensitive proportional counter (PSPC) , a convex-type background line is obtained because of the geometrical problem and the absorption of x-rays. Such phenomenon is remarkable when a wide angular range is set on a linear PSPC and it is, in particular, necessary to correct with a straight background for accurate measurement of diffraction angle or half-value breadth of the broadened diffraction profile.

External X-ray total reflection occurs when collimated X-ray beams impinge on a smooth, flat surface of matter at a small glancing angle, typically a few mrad. With respect to the X-ray fluorescence technique, total reflection experiments have allowed the trace determination of solution samples using an X-ray mirror as a sample support. The grazing incidence X-ray fluorescence technique (GIF) is also suitable for near-surface element analysis of the material, because the penetration depth of X-rays is 10-1000 Å around the critical angle.

Applications to nonmetallic specimens such as minerals will be shown and the special techniques required for such specimens described. These include coating the surface with a thin conducting layer and prepho to graphing to map out the areas of interest. Specific examples of copper-iron minerals will be given. Other applications to metallic systems such as mass transfer studies in liquid metal cooling systems will also be shown.

The x-ray fluorescence (XRF) method is well known for its capability to perform fast and accurate quantitative analysis for all elements with atomic numbers greater than ten. Energy dispersive x-ray fluorescence (EDXRF) adds to this capability the benefit of quick qualitative analysis, due to its simultaneous sensitivity to all the elements. The method has the potential for rapid and complete chemical analysis of any sample which arrives on the analytical chemist's doorstep. Although the method has been a productive tool for fast and accurate repetitive analysis of similar samples, its applicability to unique unknowns has been rather limited. The limitation arises from the usual need to calibrate the instrument's response with a set of 6 to 12 standards, whose compositions must be similar to the unknown sample. Anyone who has struggled to develop and maintain such a suite of accurately certified standards knows that a great deal of effort and expense is involved. This effort is well justified when the analyst expects to analyze the same type of material frequently over an extended tine period. However, for a unique sample analysis, the task of developing a suite of similar standards simply makes the analysis impractical. What is needed is a method that requires minimal standards, or uses no standards at all.

The Digital Equipment Corporation (DEC) operating system RSX-11M has recently been installed on a DEC PDP 11/34 computer which is used for the control of, and to acquire and process data from, three X-ray diffractometers, one X-ray fluorescence analysis unit and an electron microprobe. The RSX-11M system replaced the modified DEC 1 - 8 User BASIC previously employed, thus replacing an operating system which was known in detail only to its writer by a system which is supported by the computer manufacturer. There are three major advantages in the use of RSX-11M over 1 - 8 User BASIC: an improved handling of program scheduling, the integration of the software driver for the computer - X-ray electronics interface into the operating system without a major modification of the latter, and the ability of RSX-11M to undertake concurrent execution of instrument control, data acquisition, and data reduction. The 11/34 - RSX-11M system has been implemented to use FORTRAN; a BASIC interpreter has, however, been added which allows users to interact on-line with the computer. A command interpreter which can accept a command line from a terminal has been included.

X-Ray diffraction measurements of MnO confirm the hypothesis that the structural temperature and the magnetic transition temperature, or Néel temperature) are the same. The usefulness of X-ray diffraction intensity data of MnO, with respect to an atomic structural refinement problem involving α-Mn powders, is discussed. Lattice constant values of MnO are listed between 100 and 310°K

The residual stress left on the fracture surface is one of the important parameters in X-ray fractographic study. It has been used to analyze fracture mechanisms in fracture toughness and fatigue tests especially of high strength steels.

In this paper, X-ray fractography was applied to brittle fracture of alumina (Al2O3) and zirconia (ZΓO2) ceramics.

While x-ray fluorescence spectrometry is a highly sensitive and highly repoducible method of analysing samples, its one weakness is its relatively low sensitivity for light elements. This is mainly due to two problems: firstly the low fluorescent yield of the low atomic number elements, and secondly to the inherent inefficiency of exciting these elements. While it is not possible to improve the fluorescent yield, considerable improvements in light element sensitivity can be achieved by improvements in x-ray tubes.

A low temperature attachment based on a miniature open-cycle Joule-Thomson refrigerator has been developed for x-ray diffractometry measurements over the temperature range from 65 - 400 K, By use of a special mounting plate, the device can be substituted for the heater assembly of a high temperature attachment and thereby utilize the available vacuum chamber and x-ray transparent beryllium window. The device is demonstrated by investigating the polymorphic phase transformations that occur in barium titanate.

The growing need for multielement analytical capability is currently being emphasized by the ever broadening governmental regulations on metallic pollutants in water sources. These new regulations cover more elements and are more restrictive in the type and amounts allowable in waste water and natural sources. For example, the California Public Health Law of 1970 states that 0.01 ppm arsenic, 1.0 ppm barium, 0.01 cadmium, 0.05 ppm manganese and 5.0 ppm zinc are the limiting concentrations of these elements in drinking water. Monitoring programs, both for compliance-enforcement and general survey work, have become a greater burden on both governmental agencies and private inductries. While trace analysis in solutions presents certain difficulties to the analytical chemist, regardless of the technique used, the results of this study indicate that x-ray analysis provides a more useful analytical tool for routine work and offers multielement capability with minimal sample preparation.

The determination of the orientation of a single crystal by Laue X-ray photographs is dependent on the identification of the indices of the spots. At the present time, the determination of indices is done by various methods, none of which is entirely systematical. A method for establishing the indices of the spots which avoids a trial-and-error approach is described here. The method is graphical, uses a specially compiled table of erystallographic angles and is not dependent on the complexity of the structure of the crystal or its symmetry. An example of the cubic system is included. With more complex crystal structures the method becomes very laborious and the help of computer methods is suggested.