Synchrotron radiation has evolved tremendously in recent decades in sources, instrumentation, and applications in materials studies. This article provides background and an introduction to the state of the art of synchrotron research as it relates to materials research, including an overview of the articles in this MRS Bulletin issue, which focus on Laue microdiffraction, high-energy x-ray diffraction on battery materials, synchrotron radiation in high-pressure research, x-ray dark-field microscopy, and x-ray absorption spectroscopy applied to energy research. The modern approach of displaying diffraction data in reciprocal-space units and the distinction between spectroscopy and diffraction are summarized. Applications and technologies are continuously developing toward technical and optical limits, combining multiple methods for an even brighter future for this field. It is now time for expert groups to begin applying multiple and different kinds of quantum beams, such as neutrons, muons, electrons, and ions, complementary to synchrotron radiation for more efficient and effective characterization of materials.

Local crystal structure, crystal orientation, and crystal deformation can all be probed by Laue diffraction using a submicron x-ray beam. This technique, employed at a synchrotron facility, is particularly suitable for fast mapping the mechanical and microstructural properties of inhomogeneous multiphase polycrystalline samples, as well as imperfect epitaxial films or crystals. As synchrotron Laue x-ray microdiffraction enters its 20th year of existence and new synchrotron nanoprobe facilities are being built and commissioned around the world, we take the opportunity to overview current capabilities as well as the latest technical developments. Fast data collection provided by state-of-the-art area detectors and fully automated pattern indexing algorithms optimized for speed make it possible to map large portions of a sample with fine step size and obtain quantitative images of its microstructure in near real time. We extrapolate how the technique is anticipated to evolve in the near future and its potential emerging applications at a free-electron laser facility.

High-energy x-ray (HEX) scattering is a sensitive and powerful tool to nondestructively probe the atomic and mesoscale structures of battery materials under synthesis and operational conditions. The penetration power of HEXs enables the use of large, practical samples and realistic environments, allowing researchers to explore the inner workings of batteries in both laboratory and commercial formats. This article highlights the capability and versatility of HEX techniques, particularly from synchrotron sources, to elucidate materials synthesis processes and thermal instability mechanisms in situ, to understand (dis)charging mechanisms in operando under a variety of cycling conditions, and to spatially resolve electrode/electrolyte responses to highlight connections between inhomogeneity and performance. Such studies have increased our understanding of the fundamental mechanisms underlying battery performance. By deepening our understanding of the linkages between microstructure and overall performance, HEXs represent a powerful tool for validating existing batteries and shortening battery-development timelines.

X-ray absorption spectroscopy (XAS) is a widely used characterization technique to explore the local geometric and electronic structures of materials with element specificity. XAS measurements are performed at synchrotron radiation sources that provide brilliant, tunable, and monochromatic energy photons. The advantages of XAS include good elemental, chemical, and orbital sensitivities, which all stem from inherent electron excitation and transition processes. XAS is categorized into soft (<2000 eV) and hard (>5000 eV) x-ray regimes, based on the incident photon energy. Soft x-rays can probe the K-edges of low-Z (atomic number) elements, including Li, C, N, O, and F, and the L-edges of 3d transition metals, whose K-edge is within the hard x-ray regime. All of these elements are essential components of energy materials. This article introduces the principle of XAS and reviews some recent applications in energy storage and energy conversion, illustrating the capabilities of XAS to investigate the fundamental properties of materials from the points of view of atomic and electronic structures, which play crucial roles in understanding the reaction mechanisms in high-performance devices.

Dark-field x-ray microscopy is a new way to three-dimensionally map lattice strain and orientation in crystalline matter. It is analogous to dark-field electron microscopy in that an objective lens magnifies diffracting features of the sample; however, the use of high-energy synchrotron x-rays means that these features can be large, deeply embedded, and fully mapped in seconds to minutes. Simple reconfiguration of the x-ray objective lens allows intuitive zooming between different scales down to a spatial and angular resolution of 100 nm and 0.001°, respectively. Three applications of the technique are presented—mapping the evolution of subgrains during the processing of plastically deformed aluminum, mapping domains and strain fields in ferroelectric crystals, and the three-dimensional mapping of strain fields around individual dislocations. This ability to directly characterize complex, multiscale phenomena in situ is a key step toward formulating and validating multiscale models that account for the entire heterogeneity of materials.