Aug 2026· MRS bulletin· Vol 51, pp. 1024 - 1038· 0 citations· 69 references
Abstract
Medium-range structure at a length scale between ~0.5 and 3 nm strongly influences the properties and phase transformations of metallic glass alloys. Electron diffraction methods based on four-dimensional scanning transmission electron microscopy are well suited for characterizing such structure using nanodiffraction with beams matched in size to the length scale of interest. Structural characterization using techniques including fluctuation electron microscopy, Ångström-beam electron diffraction, and angular correlation mapping have revealed widespread competition between crystalline and noncrystalline order, structural motifs responsible for crystallization and glass formation, and length scales controlling plasticity. Time-resolved, in situ electron correlation microscopy has demonstrated spatially heterogeneous dynamics in supercooled liquids and glasses and has hinted at connections between structure and atomic motions. Continued advances in techniques, sources, and detectors offer prospects for more discoveries to come. Electron nanodiffraction probes only a few hundred atoms at a time, offering unique views of the atomic structure and dynamics of metallic glasses Electron nanodiffraction probes only a few hundred atoms at a time, offering unique views of the atomic structure and dynamics of metallic glasses
In this article, we discuss the challenges in assessing dynamics and structural changes of metallic glasses as amorphous out-of-equilibrium materials by means of coherent x-ray scattering. We focus on the fundamental understanding of the x-ray photon correlation spectroscopy (XPCS) technique and on how such an experimental probe may facilitate a deeper quantitative understanding of the underlying structural fluctuations occurring within the amorphous solid. Furthermore, we present how atomistic simulations and simulated x-ray photon correlation spectroscopy experiments can guide the interpretation of experimentally measured data. We conclude with a broader perspective on how contemporary advances in modeling, detector technology, and high flux x‑ray sources are transforming the study of glassy dynamics, enabling access to wider time and length scales and thus offering new avenues to probe the broad relaxation spectrum and complex nonequilibrium relaxation processes characteristic of amorphous solids. The X-ray photon correlation spectroscopy method uses coherent X-ray to probe structural relaxation processes in bulk metallic glasses by studying the temporal correlations in the obtained speckle patterns The X-ray photon correlation spectroscopy method uses coherent X-ray to probe structural relaxation processes in bulk metallic glasses by studying the temporal correlations in the obtained speckle patterns
P. Derlet, B. Riechers, R. Maaß· MRS bulletin· 0 citations
When cooling towards a ferroelectric phase transition, collective atomic motions (phonons) slow down (soften) until a static atomic displacement pattern forms, giving rise to spontaneous polarization throughout the material1. However, in quantum paraelectrics such as strontium titanate (SrTiO3), long-range ferroelectric order does not develop at low temperatures due to persistent quantum fluctuations of ionic positions2,3. In SrTiO3, quantum paraelectricity emerges below Tq ≈ 40 K refs. 4, 5–6 and is preceded by anomalous phonon dynamics: a transverse acoustic phonon mode partially softens at a finite wavevector, hinting at a modulated state at the nanoscale7, 8, 9, 10, 11–12. The precise real-space structure of SrTiO3 at low temperature, however, has remained unresolved despite decades of study. Here we directly image the low-temperature polar structure of a SrTiO3 lamella using cryogenic scanning transmission electron microscopy down to 20 K. High-resolution imaging reveals a spatially fluctuating landscape of nanoscale domains. Below about 105 K, short-range polar domains initially self-organize into a periodic structure extending over tens of nanometres; however, upon entering the quantum paraelectric regime below Tq, the process reverses and the periodically ordered polar nanodomains fragment into smaller clusters. Quantum paraelectricity in SrTiO3 underlies remarkable properties, including large dielectric permittivity13,14, proximity to ferroelectricity15,16, multiferroicity17 and unconventional superconductivity18, 19–20. Our visualizations suggest that these phenomena may be linked to complex ordering and disordering of polar nanodomains at low temperature. Cryo-STEM reveals that SrTiO3 forms periodic polar nanodomains below 105 K, but these fragment below 40 K, linking quantum paraelectricity to nanoscale polar ordering and disordering.
Yang Zhang, Suk Hyun Sung, Nishkarsh Agarwal et al.· Nature· 1 citation· ⚡1
Oxide interfaces, characterized by the interplay of dissimilar lattices, orbitals, charges, and spins, exhibit a wealth of emergent phenomena, such as superconductivity, two-dimensional electron gases, and magnetoelectric coupling, which hold great promise for next-generation integrated functional devices. Here, we demonstrate the formation of antiphase boundaries (APBs) near a BiFeO3/KTaO3 interface prepared by pulsed laser deposition, which further alters the local polarization features and promotes the formation of charged domain walls in BiFeO3. Using high-angle annular dark-field scanning transmission electron microscopy combined with atomic-resolution energy-dispersive X-ray spectroscopy, the atomic structures and chemical compositions of these APBs were elucidated, featuring both planar and stepped configurations. High-temperature pretreatment of KTaO3 substrate facilitates a formation of controlled depletion of K+ ions at the surface, which further drives the diffusion of Bi3+ into the substrate and helps the nucleation and stabilization of APBs. Furthermore, the built-in electric field generated by these charged APBs profoundly alters the local polarization, inducing the formation of charged domain walls above the APBs. Our findings not only reveal a mechanism for creating APB configurations under defined conditions but also offer insights into how interfacial chemistry can be leveraged to manipulate microstructures.
T. Shi, Jiaqi Liu, Shuang Chen et al.· ACS Applied Materials and In...· 0 citations
Did you know that the strongest known engineering alloy is a metallic glass? This and many other world records have emerged along the success story of amorphous metals. With their unique structural and functional properties, and arising from a vast structural design space, metallic glasses are the amorphous counterpart to the high-entropy alloys paradigm. Sixty years after their discovery, metallic glasses have matured to industrial applications, but our structural understanding remains far behind. Presently, the advent of novel structural and dynamical probing methods, combined with new theoretical and modeling approaches, allow for the first time a one-to-one mapping of structure and structural dynamics. These developments emphasize medium-range order, extended network formation, and distinct structural partitioning in long-sought depth and detail for atomically disordered solids. Such a new view on metallic-glass microstructure and dynamics bears the promise of unifying numerous macroscopically observed phenomena, including negative creep, enthalpy recovery, stress-driven rejuvenation, and many more. This issue of MRS Bulletin aims at highlighting these advances, their promise to predictively understand macroscopic behavior, and to formulate reliable descriptors for structure and dynamics and for structure–property relationships of glassy materials. Metallic glasses are outstanding metallic alloys that combine the best properties from glassy solids and crystalline engineering alloys. This article introduces the current state-of-the-art and projects the future of structure and dynamics research of metallic glasses. As an overview article, it sets the stage for a series of subsequent focused contributions in this special issue Metallic glasses are outstanding metallic alloys that combine the best properties from glassy solids and crystalline engineering alloys. This article introduces the current state-of-the-art and projects the future of structure and dynamics research of metallic glasses. As an overview article, it sets the stage for a series of subsequent focused contributions in this special issue
Ligand-mediated colloidal synthesis enables controlled growth of metal nanoparticles with properties distinct from their bulk counterparts, yet direct access to their atomic-scale surface structure remains limited. Here, we achieve atomically resolved imaging and spectroscopy of individual wet-synthesized gold nanocubes using ultrahigh vacuum scanning tunneling microscopy and spectroscopy. Following solution phase ligand removal, atomically resolved topographies reveal an unreconstructed Au(100)-(1 × 1) surface on the top cubic facet in ultrahigh vacuum. Upon annealing, quasi-hexagonal reconstructed domains emerge, coexisting with the (1 × 1) phase. Besides structural transition, scanning tunneling spectroscopy reveals an unoccupied surface-state resonance near +1.2 eV of unreconstructed Au(100) surface, which is locally modified by the reconstruction, defects, and ligand residues, thereby correlating the local electron density of states with the heterogeneous atomic structure. Field-emission spectroscopy reveals systematic lowering of the work function in the ligand covered regions. Complementary vibrational action spectroscopy further reveals the C-H stretching mode of the residual ligands. Together, these results establish an atomically precise platform directly linking colloidal synthesis to nanoscale structural, electronic, and vibrational characterization of nanomaterials.
Weike Quan, Liya Bi, Athena Aber et al.· Journal of the American Chem...· 0 citations
Interfacial structure and its evolution play an important role in determining the functional properties of advanced materials and devices. However, real oxide heterointerfaces are typically far more complex than idealized abrupt boundaries; thus clarifying how interfacial structures evolve and how such evolution affects physical properties is essential. In this work, NiO/Cr2O3 heterostructures were epitaxially grown on single-crystalline SrTiO3 substrates by pulsed laser deposition under different deposition temperatures and subsequent post-annealing treatment, both of which strongly influence the thermally driven interfacial evolution. Interfacial structures were comprehensively characterized by high-resolution X-ray diffraction and transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy. The evolution is revealed as a transition from an ultrathin interfacial transition zone in the as-deposited NiO/Cr2O3 heterostructure to the formation of a NiCr2O4 reaction interlayer, and finally to a NiO/NiCr2O4 bilayer after high-temperature annealing. Magnetic hysteresis loops measured by a superconducting quantum interference device reveal that all heterostructures exhibit weak ferrimagnetism, accompanied by a non-monotonic change in saturation magnetization with interfacial structural changes. These findings demonstrate that thermally controlled interfacial reactions and structural evolution can generate distinct magnetic characteristics, thereby providing a practical strategy for material interfaces design and performance engineering in functional oxides.
