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High-Resolution

Three-Dimensional X-Ray Microscopy

Bennett C. Larson and Bruno Lengeler, Guest Editors Abstract This issue of MRS Bulletin focuses on the rapid progress that is ongoing in the development of hard x-ray microscopies with three-dimensional spatial resolutions ranging from micrometers to nanometers. The individual articles provide a crosscut of developments in hard x-ray projection tomography microscopy for imaging density and chemical fluctuations in crystalline and noncrystalline materials; large-angle diffractionbased, spatially resolved imaging of local structure, orientation, and strain distributions in crystalline materials; and emerging coherent diffraction imaging for nanometer-range Fourier transform imaging of crystalline and noncrystalline materials. Keywords: microbeams, microstructure, three-dimensional x-ray microscopy, tomography, x-ray optics.

The availability of high-brilliance synchrotron x-ray sources, recent developments in high-precision x-ray focusing optics, and the development of new x-ray diffraction and contrast imaging techniques have stimulated revolutionary advances in three-dimensional x-ray microscopy using hard (e.g.,
5–6 keV) x-rays. Electron microscopes have long provided highresolution structure and spectroscopy tools for the investigation of thin-section samples, and electron backscattering diffraction (EBSD) microscopy routinely provides surface or near-surface microstructural information.1 Similarly, soft x-rays (e.g., 3–5 keV) enable a rich variety of twodimensional structure and spectroscopic microscopy tools.2 However, hard x-ray microscopy tools to probe the interior of bulk materials with three-dimensional spatial resolution in the micrometer or submicrometer range have, until recently, been missing from the scientific toolbox for structure and spectroscopy investigations. Considering that almost all technological and biological materials are inhomogeneous on length scales ranging from nanometers to millimeters, nondestructive probes with a range of penetration power and resolutions are needed for the investigation of the structure and evolution of

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materials. With single-crystal diamond and silicon as notable exceptions, the important technological properties of materials are often linked directly to inhomogeneous density and chemical distributions or to crystal grain-size and grain-orientation distributions; grain-boundary configurations and crystalline or noncrystalline second phases can be important as well. The generation and control of the evolution of such microstructural features are of central importance to the structural metals and ceramics industries, and they play critical roles in determining the properties of materials such as composites (hard/soft), functionally graded materials, and layered materials. The articles in this issue of MRS Bulletin describe hard x-ray microscopy techniques that provide 3D spatial resolution ranging from a few micrometers to nanometers. The individual articles include (1) x-ray absorption and phase contrast