Ten compounds are found in the Ba0-Y203-CuOx system. High temperature (≈950-1000°C) phases identified as Ba4Y2O7 , Ba2Y2O5 , Ba3Y4O9 , BaY2O4 , Y2Cu2O5 , BaCuO2+x, Ba3YCu2OZ BaY2Cu05 and BazYCu306+x are formed in this temperature range. In addition, a new compound with composition of 2BaO:CuO, which possibly has a melting point below 950°C, was prepared at 850°C. A summary o£ the crystallographic data of these 10 phases is given. In particular, results of x-ray studies pertaining to four compounds, BazYCu306+x, which is currently the most promising high To' superconductor material, Ba2Cu03 , BaY2Cu05 , and Ba3YCu20Z are reviewed.

The Powder Data File (PDF) contains far fewer organic entries than inorganic ones despite the existence of many more organic compounds. The ready availability of many of the missing organic substances affords their potential inclusion via quality experimental patterns. Considerable expansion of the organic portion of the PDF is also available via computation from the extensive published single crystal literature. Careful comparison of calculated and experimental patterns can be quite useful in resolving problems encountered in patterns from each source and ir more fully characterizing "real-life" materials. Examples of this interplay are presented, featuring, particularly, explosive compounds, an especially sparsely populated portion of the PDF.

A recent goal of the ANL Intense Pulsed Neutron Source (IPNS) has been the fabrication of a new enriched uranium target with increased neutron flux (by a factor of 3) which is dimensionally stable under irradiation. Neutron diffraction, using several instruments both at IPNS and MURR, has been used as a probe to characterize the target material vith respect to grain size and preferred orientation. The samples studied were portions of the uranium discs (4" diameter X 1/2" thick) which, when stacked, form the target assembly at IPNS. The old target discs were fabricated as slices from a fast cooled casting (arc-melted, water cooled in a cylindrical mold) and possess small grain size and negligible orientation. The new enriched target discs, on the other hand, are being fabricated from a slow cooled material (graphite book-mold, natural cooling) and, prior to additional treatment, have a large grain size and a high degree of preferred orientation which could produce dimensional changes during fission as the target is used. Our conclusion from this investigation is that a β-phase heat treatment (quench from 730°C) is necessary to produce a finer grain and more nearly random texture in thg new enriched material. Based on our detailed texture measurements the anticipated target lifetime of several years appears feasible.

We have been using the technique of pulsed neutron powder diffraction to study several problems in the physics and chemistry of the actinide elements. In these elements one often encounters very complex structures resulting from polymorphic transformations presumably induced by the presence of 5f-electrons. For exampie, at least five distinct structures of plutonium metal are found between room temperature and its melting point of 640°C, and two of the structures are monoclinic! Single crystals are usually not available, and the high resolution which is intrinsic to the time-of-flight powder technique is a powerful tool in the solution of complex structural problems. The relatively low absorption coefficients for neutrons for at least some actinide isotopes is an advantage when surface oxidation is a problem (as in high-temperature experiments) and provides good particle statistics so that high-quality data are available for Rietveld refinement. The low absorption of neutrons by other materials such as vanadium and fused silica enables the use of these materials for the containment of samples in high- and low-temperature environments, and the fixed geometry of the time-of-flight technique simplifies the design of furnaces and cryostats.

An asymmetrically cut single crystal is, generally, a large flat X-ray monochromating crystal whose principal surface has been cut an angle to the diffracting planes being utilised.

The use of such a crystal was suggested by Stephen and Barnes in 1935 as a means of obtaining a narrow intense beam of monochromatic X-rays. Fankuchen was first to demonstrate this effect experimentally. A number of symmetrically cut mosaic single crystals, including lithium fluoride, was studied by Evans, Hirsch and Kellar and by Gay, Hirsch and Kellar in the beam condensing (beam narrowing) mode only.

X-ray characterization of single crystal materials in the form of thin layers can be accomplished with the use of a double crystal diffractometer. The resultant rocking curve is a convolution of the Bragg reflection from both the first and second crystals. The width of the rocking curve at half-height is a measure of the crystal perfection of a materiel. Since the FWHM for the material being analyzed cannot be less than that of the first crystal (Monochromator), the first crystal should be of very good crystal quality. The problem that arises with the two crystal parallel configuration (Fig. 1) is that the monochromator crystal must be changed each time a material of different orientation or stoichiometry with different resultant lattice constants is analyzed. This requires changing the monochromator and re-aligning the double crystal diffractometer.

An X-ray/Laser technique is described for producing Laue patterns on very small (1mm2) crystal surfaces where it is otherwise not possible to mechanically align the surface of the crystal perpendicular to an X-ray beam. This technique has been used to determine the orientation of the diamond inserts in cutting tool bits.

The instrument employs a fully-focussing optical system which allows a wide range of sample-orientations and thus permits determination of the preferred-orientation distribution-function. Hence, measured peak-intensifies can be corrected for non-randomness.

The sample performs a planetary motion around the focus of the primary, monochromatic beam. The angle of incidence can be varied over a wide range of values, including both transmission and reflection. The sample can be rotated in its own plane in a controlled manner. Full illumination is obtained in any position of the sample. The diameter of the Rowland-sphere of the powder-optics remains constant and permits the use of a sphericai sample-layer.

A Search/Matcti program lias 'beea written for the IBM PC AT computer that is capable of -using "background - subtracted, digitized 2-ray powder diffraction scans as inputs in addition to the d/I data traditionally used. This novel procedure has proved especially effective when numerous unresolved lines are present in the pattern. The method is also less demanding of data quality thaii the peak location programs. The program may he extended to searching & data "base of digitized standard patterns.

The program, has several parameters that can- "be adjusted, including chemistry. The results from the Johnson/Vand list type of output are directly accessible to the interactive graphics program. This gives the diffraction!st a fast method for verifying the phase identification. Because of the speed of fixed point computation techniques, the 52,791 pattern file can be scanned in about 90 seconds.

This paper will illustrate the utility of the program.

This paper discusses the use of a personal computer in the x-ray diffraction laboratory. DARC (Digital Automated Hocking Curve) Topography is a system in which a PC is used extensively. Using this system as an example, the tsany uses and benefits of the PC as a tool will be explained.

Energy dispersive x-ray fluorescence (XRF) spectrometry has been used extensively for some time now to do accurate and rapid analysis of a variety of samples. Most XRF Systems today use cryogenically cooled Si(Li) detectors to obtain the resolution needed for analysis of samples containing several elements. The need for the cryogenic coolant results in these XRP systems being rather large and not readily adaptable to portable devices. Detectors that require no cooling, or at least require only cooling obtainable by electrical weans, offer a definite advantage over cryogenically cooled detectors for use in portable devices. Mercuric iodide (HgI2) detectors are one type of such room-temperature detectors. The major disadvantage of any room-temperature detector has been the poor eneygy resolution associated with them.

An uniform field gas proportional scintillation counter is described for X-ray fluorescence analysis applications requiring large window areas and good energy resolution at rcom temperature. This counter uses continuously purified xenon as the filling gas and a 1 inch diameter window. A quartz window Hamamatsu R562 photomultiplier is used with its window in direct contact with the gas. Measured energy resolutions were in the 12 to 13% range for the 5.9keV X–ray line. X–ray fluorescence spectra for a few samples are presented with excitation by ImC 55Fe and 244cm sources. Measured physical excitation-detection efficiencies are compared with calculated values.

One of the strongest analytical qualities of energy-dispersive x-ray fluorescence (EDXRF) is the wide range of analyte elements that can be detected and analyzed. Historically, the technique has covered all the elements from sodium (Z=11) and above. A useful measure of specific spectrometer performance is analyte sensitivity. X-ray spectrometric sensitivity is usually expressed in terms of minimum detectable amount of analyte or rate of change of analyte line intensity with change in amount of analyte. Many factors affect analyte sensitivity in EDXRF. These include excitation conditions, specimen conditions, system geometry, atmosphere, detector and readout conditions, and of course the specific analyte line. Typically, EDXRF sensitivity is very good, and low ppm concentrations of analytes are routinely analyzed–until one encounters the light elements.

The efficiency dependence on detector window area for three different geometries of source excited energy dispersive X-ray fluorescence (EDXRF) analysis systems are calculated using the Monte Carlo method. Two typical samples (coal and oil) are considered for discussion. The results show that the efficiency is affected mainly by geometric factors: source-to-sample distance and absorption of the exciting X-rays; fluorescent photon self-absorption has a much smaller effect.

A new analysis principle for energy-dispersive X–ray fluorescence has been identified and investigated as to feasibility. It consists of: (1) generating the complete spectral response for a sample of known (assumed) composition by Monte Carlo simulation,(2) keeping track of the individual elemental responses within the Monte Carlo simulation for use as library spectra, (3) use of the library least–squares (linear) analysis method to obtain the elemental amounts for any unknown sample spectrum, and (4) iterating these steps if the unknown amounts are too fax from the assumed composition originally used.

This principle has been investigated for a radioisotope source excited EDXRF system consisting of a 109Cd source and a Si(Li) detector for a Cu-Ni alloy sample (CDA Alloy 715) and a stainless steel sample (304 Stainless Steel) and found to give excellent results. This analysis principle makes unique use of the Monte Carlo “forward” simulation method to provide the elemental library spectra for use in the library least-squares method of analysis.

The concepts underlying the definition and calculation of fundamental influence coefficients and their role in the computation of derived coefficients in alpha-type algorithms are examined. The fundamental-parameter method initiated and continues to provide the basis for the steady progress in giving influence coefficients a sound theoretical status. New definitions of fundamental influence coefficients as the prorating of monochromatic coefficients on the basis of the intensities of each elementary contributions as a function of the total fluorescence intensity and of the intensity of the pure analyte are compared to the presently used approach of defining coefficients as a function of total absorption only.

Appearance potential spectroscopy has been practiced for many years. In essence, it simply involves ramping the energy of the exciting quanta across excitation edges and observing the onset of a signal. Because of the relative simplicity with which the energy can be controlled, electrons have been the conventional quanta employed. The signals which have "appeared", characteristic of the atoms being studied, have been either Auger electrons or x-ray. The literature is replete with references to appearance potential measurements; the applications have, for the most part, demonstrated interesting physics, but analytical measurements have not been numerous.

The X-ray external total reflection was used for the x-ray fluorescence analysis of the near surface layer of a GaAs wafer and a GaAlAs epilayer. Synchrotron radiation was used as an excitation source. The intensity ratio between the Ga K and As K fluorescence signals was measured as a function of the glancing angle. The reduction of As atoms near the surface of less than a hundred Å was observed for the high temperature annealed GaAlAs epilayer.

A scantling X-ray fluorescence(XRF) microprobe using WoIter type 1 optics was developed, and micro and trace element analysis was carried out using synchrotron radiation up to 10 keV as an excitation source. The design parameters of the optical system and the performance of the system, such as the beam size and the intensity, are described. The MDL obtained for Mn was 6 ppm in relative concentration and about 0.1 pg in absolute amount. The estimated spatial resolution was better than 10 um.

In on–stream X–ray fluorescence analysis of ore slurries, the effects due to variation in the particle-size of solids can cause appreciable and sometimes major errors in the measured concentration of an element to be determined. Weight percentage of slurry ore grains with diameter smaller than 75 um (called later W75) is commonly used as measure of ore fineness and can be determined using particle-size analyzers. A method of correcting for W75 variaition is highly desireable, particularly in a case when high analysis accuracy is required for economical reasons.