By measuring the diffuse scattering signal from binary alloy single-crystals over a range of temperatures, one can determine the parameters for configurational local ordering, thermal, and lattice distortions. Using a combination of high-energy x-rays, a specially-designed sample chamber, and a two-dimensional detector, high-quality in-situ measurements can be completed in a time-frame of tens of seconds. The high-energy x-rays illuminate a large volume of bulk material and are scattered in transmission geometry. Because the signal of interest is weak, a sample chamber was designed to suppress the background. Collecting 2D ../images over different crystal orientations permits complete 3D determinations of the short-range order correlations and lattice distortions for the binary alloys. This experimental method vastly improves upon the previous generation of diffuse scattering measurements, where reflection geometry and a point counter were used to collect data in a time frame of days at a single temperature.

As a demonstration of this new diffuse scattering method, the examples of Ni55Pd45 and Ni25Pd75 follow. The measurements were made at many temperature (from room temperature up to 920°C) and along the (100) direction of the fcc-crystal. In the figure below, the differences in scattered intensities can be seen for the two compositions and three temperatures. As the temperature increases, the contribution from the thermal diffuse scattering increases. Altering the chemical composition effects the contributions from the lattice distortions and short-range ordering.

Diffuse scattering from Ni55Pd45 (top) and Ni25Pd75 (bottom) for three temperatures.

Reciprocal space analysis of the diffraction patterns is carried out for each temperature and composition using seven independent parameters to encompass the short-range-ordering parameters, static lattice distortions, and thermal parameters. A comparison between the measured and calculated scattering is shown in this second figure. The contributions of the different components are also shown.

Diffuse scattered intensity for Ni55Pd45 at 410°C; a) comparison of the measured and experimentally-determined calculation and their difference (Δ) between the two; the calculated components of: b) thermal diffuse scattering, c) static lattice distortions, and d) short-range ordering.

Mezger M., Reichert H., Ramsteiner I.B., Udyansky A., Shchyglo O., Bugaev V.N., Dosch H., Honkimäki V. - Temperature and concentration dependence of the effective pair interaction parameters in Ni-Pd from high-energy X-ray diffuse scattering - Phys. rev., B 73, 184206-1-184206-14 (2006).
Ramsteiner I.B., Schöps A., Phillipp F., Kelsch M., Reichert H., Dosch H., Honkimäki V. - High-energy X-ray and transmission electron microscopy study of structural transformations in Ti-V - Phys. rev., B 73, 024204-1-024204-7 (2006).
Reichert H., Schöps A., Ramsteiner I., Bugaev V.N., Shchyglo O., Udyansky A., Dosch H., Asta M., Drautz R., Honkimäki V. - Competition between order and phase separation in Au-Ni - Phys. rev. lett. 95, 235703-1-235703-4 (2005).
Reichert H., Bugaev V., Shchyglo O., Schöps A., Ramsteiner I., Sikula Y., Dosch H., Honkimäki V. - Reply: Strain-induced nonanalytic short-range order in the spin glass Cu83Mn17 - Phys. rev. lett. 88, 209604-1 (2002).