The diffusion coefficients of oxygen (D) in thin films of amorphous (a-) and nanocrystalline monoclinic (Hf,Zr)O-2 are determined by profiling the long-range diffusion of the stable oxygen isotope (O-18) in the temperature range of 300 degrees C-700 degrees C using secondary-ion mass spectrometry. D at 300 degrees C-400 degrees C in the a-phase and D at 500 degrees C-700 degrees C in the m-phase exhibit a nearly continuous temperature dependence. The activation energy for diffusion in the a-phase is found to be 1.42-2.91 eV, depending on the degree of structural relaxation, and is comparable to or higher than that for volume diffusion in the m-phase (0.48-1.59 eV, including literature data). The pair distribution functions for the a-phase, obtained using electrons as a probe, indicate that the local structure resembles that of an m-phase model from a previous molecular dynamics simulation. Supported by previously reported theoretical calculations, the possible diffusion mechanisms of oxygen in both the a-phase and m-phase are discussed.

The development of radiation-tolerant materials is of technological importance for establishing safe operating systems in the nuclear industry, from power generation to the immobilization of high-level radioactive waste. Harsh radiation environments generate interstitials and vacancies in materials, and their accumulation leads to structural changes, including order-to-disorder phase transformations and amorphization. These structural changes are induced locally on an atomic scale; therefore, transmission electron microscopy is a useful technique for analyzing radiation effects in materials. In addition, the strong interaction between matter and electrons enables the detection of weak signals associated with phase transformations, such as diffuse scattering and halo rings. This article provides an overview of radiation-induced amorphous structures in materials consisting of light elements, such as boron carbide and silicon oxycarbide, as well as the short-range ordered structure that appears during an order-to-disorder phase transformation in fluorite structural derivatives.

High-level radioactive waste requires long-term isolation, motivating the development of durable materials beyond conventional glass matrices, which are thermodynamically metastable. Crystalline ceramics, particularly fluorite-derived oxides, are promising due to their stability, radiation tolerance, and capacity to incorporate radionuclides. In this study, we performed swift heavy ion irradiation into β-Sc2Hf7O17, one of the fluorite structural derivatives in the Sc2O3–HfO2 pseudo-binary system, and investigated its order-to-disordered phase transformation by transmission electron microscopy (TEM). The rhombohedral ordered β-phase transformed into a cubic disordered phase due to damage accumulation. Electron diffraction experiments and dark-field TEM observations revealed the formation of an intermediate phase with an ordered structure distinct from both the β-phase and the other equilibrium phases present in the phase diagram. Irradiation-induced evolution in these materials is complex, involving not only disorder and amorphization but also the formation of intermediate ordered phases and nanoscale heterogeneity. Model systems such as β-Sc2Hf7O17 provide insight into these processes, revealing that local ordering can persist or re-emerge under irradiation, potentially enhancing defect accommodation and delaying structural degradation. This highlights the importance of understanding defect dynamics, local structure, and interfacial effects in designing radiation-resistant waste forms capable of maintaining integrity over geological timescales.

Abstract YBa 2 Cu 3 O 7-x (YBCO) thin films doped with BaHfO 3 (BHO) at different concentrations were prepared on a SrTiO 3 substrate using pulsed-laser deposition, and their structures were investigated using transmission electron microscopy and scanning transmission electron microscopy. In the 3 vol.% BHO-doped YBCO thin film, continuous BHO nanorods extended from the substrate to the surface. In contrast, thick, fragmented BHO nanorods with larger diameters formed near the surface of the 7 vol.% BHO-doped thin film. Both thin films contained precipitates, which increased in size with the BHO concentration. These results suggest that inhomogeneity in the microstructure becomes more pronounced with increasing BHO concentration.

Self-organization realizes various nanostructures. Conventional self-organization is along the growth direction, resulting in a symmetric nanostructure. Asymmetric self-organization is demonstrated in strain-controlled phase separation.

ZrN is a model system used to understand the irradiation response of isostructural advanced nuclear fuel, UN. UN possesses desirable material properties, such as improved thermal conductivity and fissile uranium density compared to oxides, but understanding damage accumulation and recovery processes in its rocksalt structure remains limited. Micro- and nanocrystalline ZrN were studied under ion irradiation using 600 key Ar+ ions with fluences varying from 1 x 1015 to 1 x 1017 ions/cm2 at room temperature. Structural parameters, crystallite size, and microstrain of crystalline phases were determined via a unique Rietveld refinement of glancing incidence XRD data. Transmission electron microscopy was used to investigate microstructural modifications, and nanoindentation was used to explore the evolution of mechanical properties. The results show a pronounced increase in the crystallite size of nanocrystalline ZrN, while induced damage degrades the coherence of scattering domains in both ZrN systems post-irradiation. Microcrystalline ZrN displays swelling with increasing fluence, whereas nanocrystalline ZrN contracts before showing a continued unit cell expansion at higher fluences. AFM was used to confirm swelling in mi-crocrystalline ZrN, while oxidation in nanocrystalline ZrN is explored using ToF-ERDA and is attributed to a radiation-induced REDOX reaction. Nanoindentation results confirmed increases in the post-irradiated surface hardness and elastic modulus. The TEM investigation provides evidence of periodic and incommensurate ordering in irradiated regions of microcrystalline ZrN. The formation of a distinct epitaxial layer of cubic ZrO2 on the surface of microcrystalline ZrN has been attributed to the effects of incident ion interactions.

In this study, Ag-doped SiO2-CaO-P2O5 bioactive glasses (BGs) were synthesized by a spray drying method, and their atomistic structures were investigated by transmission electron microscopy, X-ray diffraction, and nuclear magnetic resonance. The constituent elements (Si, Ca, P, and O) were homogeneously distributed in the pure (non-doped) BG, but a small Ca- and P-rich layer was present on the surface. The segregation of Ca and P on the surface became more pronounced with increasing Ag concentration. The atomic pair-distribution functions extracted by nanobeam electron diffraction revealed that the Ag-doped BG particles had a heterogeneous amorphous structure: the interior and surface of the BG particles were similar to those of SiO2 and phosphate-based glasses, respectively. The addition of Ag resulted in less non-bridging oxygen, which may be due to the removal of the network modifier ion (Ca) from the SiO2 network. In vitro bioactive tests of the pure BG and Ag-doped BG particles revealed that the formation of hydroxyapatite was enhanced by Ag doping, although the amount of non-bridging oxygen decreased. This is attributed to the P- and Ca-rich surface layer, which triggers the nucleation and growth of hydroxyapatite. (c) 2025 Published by Elsevier B.V. on behalf of The Society of Powder Technology Japan. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

To improve the critical current density of c-axis oriented YBa2Cu3O7 (YBCO) thin films, much effort has been devoted to the introduction of pinning centers that disrupt vortex migration under magnetic fields. Threading dislocations are anticipated to act as one-dimensional pinning centers without reducing the superconducting regions. In this study, YBCO thin films were prepared on a SrTiO3 (STO) + xCeO2 (x = 0%, 30%, and 50%) buffer layer by pulsed-laser deposition, and their nanostructures were analyzed by transmission electron microscopy. The interface between the buffer layer and the YBCO thin film was flat for the pure STO, while it was roughened by numerous nanoparticles for the CeO2-doped buffer layer. Due to these nanoparticles, threading dislocations were introduced more densely in the YBCO films on the STO + CeO2 buffer layer than in those on the pure STO buffer layer, depending on the volume percent of CeO2. Investigations of the critical current density as a function of the magnetic field revealed that the threading dislocations effectively act as pinning centers.

We report a giant spin-orbit torque (SOT) induced by spin Hall effect (SHE) in amorphous Pt(P) alloys, which is confirmed by magnetization switching and spin torque-ferromagnetic resonance measurements. Pt(P) is fabricated by ion-implantation technique using energies from 10 to 30 keV with doses ranging from 2.5 × 1016 to 10 × 1016 ions/cm2. The P-ion implantation process causes distortion and defects in the fcc structure of the as-deposited Pt layer and changes it to an amorphous structure as the accelerating energy as well as the dose increases, leading to a decrease in the electrical conductivity. However, we can obtain a higher spin Hall conductivity, σ_xy^SH of 3.62×10^3ℏ/2eΩ^-1cm^-1 for Pt(P) as compared to that of 1.03×10^3ℏ/2eΩ^-1cm^-1 for pure Pt. The spin Hall efficiency, θ_SH is drastically increased up to 1.17 for Pt(P) with 30 keV energy and dose of 7.5 × 1016 ions/cm2. We also observe a significant reduction in the critical switching current density, J_sw of the SOT magnetization switching from 1.5 × 1011 A/m2 for pure Pt to 3.0 × 1010 A/m2 for Pt(P). Such a giant SHE can reduce the power consumption to control the magnetization by using SOT, and therefore our findings may provide an alternate path to enhance θ_SH by using amorphous materials with a variety of elements, beyond crystalline solids. The spin-orbit torque τ_DL arising from spin Hall effect is often constrained by low values of spin Hall efficiency θ_SH . In this work, introducing phosphorus (P) into platinum (Pt) by ion implantation, thereby forming Pt(P), a significant increase in θ_SH is found. This, in turn, leads to a reduction in the charge current density J_DC for magnetization switching. This new amorphous material achieves a remarkable 34-fold increase in θ_SH , from 0.034 (pure Pt) to 1.17, making it a strong candidate for energy-efficient spintronic devices and offering a pathway beyond conventional crystalline solids.

The nanorods are effective in improving the critical current density in YBa2Cu3O7 films, but their pinning strength and morphology depend on the fabrication process. To understand the critical current density mechanism, the vortex excitation mode as well as static pinning configuration should be discussed. In this study, we prepared YBa2Cu3O7 + BaHfO3/YBa2Cu3O7 composite multilayers (CMLs). This is a segmented nanorod system where the length of nanorods can be controlled. Two types of CMLs were fabricated to extract the influence of the pinning strength of the nanorods, where the nanorod pinning strength is relatively represented by Jc(77 K,1T) of a YBa2Cu3O7 + BaHfO3 single layer film: 0.73 MA cm-2 for strong-pinning nanorod and 0.08-0.27 MA cm-2 for weak-pinning nanorod. In the multilayer with strong-pinning nanorods, the critical current density decreased with increasing the pure layer ratio, indicating that the vortex excitation from the nanorods was accelerated by the pure layer. In the multilayer with weak-pinning nanorods, dependence of the critical current density on the pure layer ratio exhibited the peak due to the competition of excitation modes. Surprisingly, when we compare the results in different types of CMLs, the critical current density for high pure layer ratio is almost the same despite different nanorod pinning strength, where the nanorod edges rather than the nanorod core is a dominant pinning center. Design of the excitation mode as well as static configuration is very effective in achieving high critical current density in YBa2Cu3O7 films.

The diffusion coefficients of oxygen ( D ) in thin films of amorphous (a‐) and nanocrystalline monoclinic (Hf,Zr)O 2 are determined by profiling the long‐range diffusion of the stable oxygen isotope ( 18 O) in the temperature range of 300°C–700°C using secondary‐ion mass spectrometry. D at 300°C–400°C in the a‐phase and D at 500°C–700°C in the m ‐phase exhibit a nearly continuous temperature dependence. The activation energy for diffusion in the a‐phase is found to be 1.42–2.91 eV, depending on the degree of structural relaxation, and is comparable to or higher than that for volume diffusion in the m ‐phase (0.48–1.59 eV, including literature data). The pair distribution functions for the a‐phase, obtained using electrons as a probe, indicate that the local structure resembles that of an m ‐phase model from a previous molecular dynamics simulation. Supported by previously reported theoretical calculations, the possible diffusion mechanisms of oxygen in both the a‐phase and m ‐phase are discussed.

The diffusion behavior of various dopants in gallium nitride (GaN) should be comprehensively understood as essential for materials design and for controlling of the electrical properties towards versatile device applications. This study measures the diffusion coefficient (D) of a typical n-type dopant, silicon (Si), along the c-axis direction in monocrystalline GaN (mc-GaN) films with the wurtzite structure at the relatively low temperature range of 600-900 degrees C compared to previous reports. Two types of samples are examined using secondary ion mass spectrometry. In the case of a thin Si layer deposited on mc-GaN, the D values are determined by analyzing the Si concentration profiles based on an error-function type equation, yielding values in the range of 5.1 x 10-21-3.0 x 10-19 m2 s-1. The activation energy for Si diffusion is 1.07 eV, which is comparable with the data reported in the literature for the measurements above 900 degrees C. In contrast, no Fickian diffusion of Si is observed in a diffusion couple of an epitaxially-grown GaN film containing Si, GaN(Si), on mc-GaN at 600-900 degrees C. Cross-sectional transmission electron microscopy reveals that the microstructure of the GaN(Si) layer is highly defective; not only do boundaries between columns exist, but numerous dislocations are also present throughout the layer, serving as trapping sites for Si.

Knowledge of radiation-induced structural changes in complex oxides is of technological importance for the development of container materials for the immobilization of nuclear waste. Fluorite structural derivatives are candidates for container materials, but their disordering processes under radiation environments are still unclear. In the present study, ion irradiation was performed on the Sc2O3-HfO2 pseudo-binary system in which fluoriterelated structural compounds such as beta-Sc2Hf7O17, gamma-Sc2Hf5O13, and delta-Sc4Zr3O12 exist, and the short-range ordered structures were investigated by transmission electron microscopy (TEM). The pristine long-range ordered rhombohedral phase was found to transform into a long-range disordered cubic oxygen-deficient fluorite phase upon ion irradiation. The atomic arrangements are not completely disordered, but a more ordered structure was present in the disordered fluorite matrix. A characteristic diffuse scattering was observed in the electron diffraction patterns, and dark-field TEM observations revealed that it is due to microdomains, defined as small regions where the degree of order is higher than that of the disordered matrix. Although the parent phase was different before irradiation, the short-range organization is the same. A comparison of diffuse scattering with the location of superlattice reflections suggested that the microdomains have a structure similar to the delta-phase. With increasing Sc2O3 concentration, the microdomains of delta-type structures were suggested to change to shortrange ordered bixbyite structures, which are not present in the equilibrium phase diagram.

In recent years, printed thermoelectric thin films have attracted attention due to their advantages in enabling large-area and flexible designs. We developed printable thermoelectric composites of bismuth telluride and halide perovskite, which were expected to exhibit superior thermoelectric properties compared to other printable materials, such as conductive organic materials. The measured dimensionless figure of merit was about 0.1 at room temperature due to its low thermal conductivity. We assessed the interfacial thermal resistance between bismuth telluride and halide perovskite using multilayered films to understand the measured low thermal conductivity. The calculated thermal conductivity using the measured interfacial thermal resistance was fairly consistent with the effective thermal conductivity observed. We also discussed the interfacial thermal resistance using a phonon transport model based on ab-initio calculations to confirm the validity of our measurements. Additionally, we found that the high interfacial thermal resistance was achieved due to the low group velocities of both materials in the composites. This mechanism can be applied not only to improve thermoelectric materials but also to address thermal issues in composites.

Fabrication of YBa2Cu3O7 nanocomposite films on silicon substrates is required for superconducting electromagnetic devices. Low-temperature deposition is effective in suppressing the chemical reaction between YBa2Cu3O7 and Si, while sufficient diffusion is required to form the well-defined nanocomposite structure. The fabrication of the YBa2Cu3O7 nanocomposite films on Si substrates should simultaneously satisfy these conflicting requirements. A YSZ (yttrium stabilized zirconia) buffer layer was epitaxially grown on Si substrates to suppress the chemical reaction. Then, the YBa2Cu3O7 + Ba2YbNbO6 films were fabricated on the YSZ/Si. The nanorods with diameters of 9-17 nm were elongated along the c-axis even at the low deposition temperature. The YBa2Cu3O7 + Ba2YbNbO6 nanocomposite film exhibited a critical temperature of 86.0 K, which is comparable to the critical temperature of 85.6 K in the pure film. The irreversibility temperature was slightly improved by the nanorods. Thus, we demonstrate the formation of nanorods in the YBa2Cu3O7 films on Si substrates without lowering the critical temperature. This opens the superconducting electromagnetic devices integrated with high-temperature superconductors and semiconductors.

Oxygen-deficient compounds A4B3O12 have a δ-type structure with a regular long-range arrangement of oxygen vacancies induced by compensation of the charge difference between A3+ and B4+ cations, while A and B cations do not order long-range and only display weak short-range correlations. The δ-type compounds in the Sc2O3-HfO2 and Sc2O3-ZrO2 systems exhibit excellent resistance to radiation-induced amorphization, but the long-range ordered δ-phase was transformed into a short-range ordered bixbyite phase. Since this structural change was not predicted from the phase diagram, the validity of the formation of the bixbyite phase and its stability are still unclear. In the present study, the changes of radiation-induced microstructures in δ-Sc4Hf3O12 under heat treatments and electron beam irradiations were examined by ex-situ and in-situ transmission electron microscopy. It was found that the ion-beam-induced metastable bixbyite phase is transformed into the δ and fluorite phases by the rearrangement of the oxygen vacancies.

To improve the thermoelectric properties of SnSe films, carrier control is required, but elemental doping is difficult due to the thermodynamic solubility limit. Isovalent elements may generate holes or electrons not in a direct manner but in the manner to form point defects. In this study, the Sn(Se,Te) films were fabricated by a pulsed laser deposition (PLD) method to control the carrier concentration by substituting isovalent Te for Se. The coexistence of the orthorhombic and cubic phases at the tens of nanometer scale in the SnSe0.5Te0.5 film was clarified by the structural observation, which is consistent with the equilibrium phase diagram. In spite of the phase coexistence, the lattice parameters linearly increased with an increase in the Te content in the Sn(Se,Te) films. This demonstrates the metastable composition situation for each phase, namely, the carrier control beyond the thermodynamic limit due to the nonequilibrium growth in PLD. As a result, the Seebeck coefficient decreased, and the electrical conductivity increased to increase the power factor, especially in a low temperature near room temperature. The Te substitution in the nonequilibrium PLD increases the hole concentration beyond the thermodynamic solubility limit and thus is effective in controlling the carrier in the SnSe films where carrier doping is difficult.