Compositionally complex oxides have garnered increasing interest for their enhanced phase stability and tunable functional properties, yet their development as bulk single crystal scintillators remains limited. Herein, we report the Czochralski growth and characterization of (Gd1/4Y1/4Tb1/4Lu1/4)3Al5O12:Ce (GYTLAG), a compositionally complex garnet incorporating four dodecahedrally coordinated principal rare earth elements. The garnet phase was confirmed by powder and single crystal X-ray diffraction, and macroscopic defects are described. X-ray absorption near-edge structure measurements confirm the 3+ oxidation state of all rare earths and support their occupation of the same crystallographic site; white line intensity variations correlate with the anticipated segregation behavior. Elemental segregation is quantified by SEM/EDS and ICP-OES, and a linear trend was established between the segregation coefficient and the difference between each rare earth's ionic radius (r) and the average ionic radius (AIR) of the dodecahedral site. This trend offers a predictive framework for compositional control in future REAG crystals grown by the Czochralski method. Photoluminescence and radioluminescence measurements reveal both Ce3+ and Tb3+ emission. Scintillation pulses exhibit four-component decay with dominant similar to 230 mu s and similar to 1.2 ms components, and the light yield is estimated to be up to 43,000 ph/MeV under 137Cs gamma-ray excitation. GYTLAG also demonstrates a strong radioluminescence efficiency and 50% lower afterglow at 20 ms compared to a LuAG:Ce reference, underscoring its promise for scintillator applications.

Excitons, which are Coulomb bound electron-hole pairs, are composite bosons and thus at low temperature can form a superfluid state with a single well-defined amplitude and phase. We directly image this macroscopic exciton superfluid state in an hBN-separated MoSe2-WSe2 heterostructure. At high density, we identify quasi-long-range order over the entire active area of our sample, through spatially resolved coherence measurements. By varying the exciton density and sample temperature, we map out the phase diagram of the superfluid. We observe the superfluid phase persisting to a temperature of 15 K, which is in excellent agreement with theoretical predictions. This works paves the way to realizing on chip superfluid structures capable of studying fundamental physical behaviors and quantum devices that use superfluidity.

Optical measurements of 2D semiconductors have primarily relied on far-field spectroscopy techniques, which are diffraction limited to several hundred nanometers. Precisely imaging nanoscale spatial disorder requires an order of magnitude increase in resolution capabilities. Here, we present a spatially resolved study of the exciton spectra of monolayer MoSe2 in the visible range using cryogenic scattering-type scanning near-field optical microscopy (s-SNOM) operating down to 11 K. Mapping the exciton resonance across an hBN-encapsulated MoSe2 monolayer, we achieve sub-50 nm spatial resolution and an energy resolution below 1 meV. We further investigate the material's near-field spectra and dielectric function, demonstrating the ability of cryogenic visible s-SNOM to reveal nanoscale disorder. Comparison to room-temperature measurements illustrates enhanced capabilities of the cryogenic s-SNOM to reveal fine-scale material heterogeneity. These results establish cryogenic visible s-SNOM as an effective nanoscale excitonic probe, offering valuable insights into 2D material heterogeneity and nanoscale sensing.

Measurement of laboratory atomic pair distribution function data has improved with contemporary X-ray sources, optics and detectors, with acquisition times of the order of minutes for ideal samples. This paper examines resolution effects in pair distribution function data obtained using a convergent-beam configuration and an Ag X-ray tube from standard silicon powder and from 10 nm BaTiO3 nanocubes. The elliptical multilayer X-ray mirror reflects a non-trivial X-ray spectrum and introduces resolution effects not commonly treated in ordinary parafocusing divergent-beam laboratory diffraction. These resolution effects are modeled using the fundamental parameters approach, and the influence this has on interpretation and modeling of the resulting reduced atomic pair distribution function data is demonstrated.

One-dimensional (1D) van der Waals materials have emerged as an intriguing playground to explore novel electronic and optical effects. We report on inorganic one-dimensional SbPS4 nanotube bundles obtained via mechanical exfoliation from bulk crystals. The ability to mechanically exfoliate SbPS4 nanobundles offers the possibility of applying modern 2D material fabrication techniques to create mixed-dimensional van der Waals heterostructures. We find that SbPS4 can readily be exfoliated to yield long (>10 μm) nanobundles with thicknesses that range from 1.3 to 200 nm. We investigated the optical response of semiconducting SbPS4 nanobundles and discovered that upon excitation with blue light, they emit bright and ultra-broadband red light with a quantum yield similar to that of hBN-encapsulated MoSe2. We discovered that the ultra-broadband red light emission is a result of a large ∼1 eV exciton binding energy and a ∼200 meV exciton self-trapping energy, unprecedented in previous material studies. Due to the bright and ultra-broadband light emission, we believe that this class of inorganic 1D van der Waals semiconductors has numerous potential applications, including on-chip tunable nanolasers, and applications that require ultraviolet to visible light conversion, such as lighting and sensing. Overall, our findings open avenues for harnessing the unique characteristics of these nanomaterials, advancing both fundamental research and practical optoelectronic applications.

The heat transfer rate of magnetocaloric regenerators is a topic of extensive research and the cyclability of these regenerators is critical to the operation of systems with a high coefficient of performance (e.g., potentially >22, significantly higher than typical vapor compression cooling technologies). To enable a high operating frequency that will result in a high specific cooling power, the heat transfer fluid should have high thermal conductivity and lower specific heat, i.e., higher thermal diffusivity. Eutectic metal alloys possess these qualities, such as gallium–indium–tin (Galinstan), whose thermal diffusivity has been found to be approximately an order of magnitude higher than water. For this study, the effects of eutectic liquid Galinstan exposure on the phase stability of LaFe13−x−yMnxSiyH1.6 magnetocaloric powders in an active magnetic regenerator device were investigated. The powders were characterized before and after exposure to Galinstan using X-ray diffraction, in which the phases were determined using the Rietveld refinement technique and X-ray fluorescence. It was found that after Galinstan exposure, hydrogen containing phases were present in the powder, suggesting that the hydrogen was lost from the magnetocaloric phase. The magnetocaloric phase degradation indicates that the powder was incompatible with the Galinstan metal in an environment with moisture.

Complementary analytical approaches were employed to probe the effect of grain size on thermally induced oxidation of zirconium carbide (ZrC) utilizing thermogravimetric analysis, differential scanning calorimetry, and Raman spectroscopy, as well as synchrotron-based and laboratory-based X-ray diffraction (XRD) experiments. The oxidation mechanism and phase behavior of nanocrystalline ZrC (grain size ~ 20 nm) were compared with that of the more documented microcrystalline ZrC (grain size ~ 1 µm). Synchrotron XRD at the Advanced Photon Source with a hydrothermal diamond anvil cell (HDAC) used as a sample chamber revealed that the onset of oxidation is at ~ 380 °C for microcrystalline ZrC which is in agreement with previous work. In contrast, the critical oxidation temperature was ~ 330 °C for nanocrystalline ZrC. Additional high-temperature synchrotron XRD experiments at the National Synchrotron Light Source II using a lamp furnace in combination with Raman analysis showed that tetragonal ZrO2 forms as an initial oxidation product and transforms at higher temperatures to the monoclinic phase. Thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC) confirmed the X-ray results of a lower critical oxidation temperature for the nanocrystalline sample. The phase transformations in the oxide phase with associated critical temperatures were also evident in the thermodynamic data as exothermic heat events.

Al100-x-y-zCexNiyMnz thin films were synthesized via combinatorial sputtering from Al, Al80Ce20, Al91Ni9, and Al93Mn7 targets. The resultant as-deposited films exhibit a continuous composition gradient of the various constituents and form a metastable solid-solution over most of the composition space. Subsequent annealing leads to the formation of the thermodynamically stable systems of Al, and alpha-Al11Ce3, Al8CeMn4, and Al23Ce4Ni6 intermetallics - where the phases present and fraction depend on the composition. Temperature dependent x-ray diffraction (TDXRD) was used to determine the coefficients of thermal expansion (CTE) for each phase. The thin film Al and Al11Ce3 temperature dependent CTE values are consistent with previously reported results. The thin film Al8CeMn4 phase reveals a slight decrease in the CTE with a range from 27 x 10-6 oC- 1 to 23 x 10-6 oC- 1 in the temperature range 25-550 degrees C. The thin film Al23Ce4Ni6 phase exhibits a CTE value of approximate to 9 x 10-6 oC- 1 near room temperature and increases to 14 x 10-6 oC- 1 at 550 degrees C. To confirm the thin film results, bulk stoichiometric Al8CeMn4 and Al23Ce4Ni6 samples were prepared and measured under similar conditions. The Al8CeMn4 bulk sample confirmed the negative CTE trend observed in the thin film sample. Compared to its thin-film counterpart, the Al23Ce4Ni6 bulk sample similarly demonstrated a low CTE value near room temperature of 5 x 10-6 oC- 1 and an anomalous minimum in the CTE at approximate to 75 degrees C, which was confirmed via temperature dependent neutron diffraction. Temperature dependent magnetic and electrical measurements were subsequently taken on Al23Ce4Ni6, and the anomalous minimum in the CTE coincided with an electronic phase transition.

Several hybrid halide 2D-perovskite species emit light with an emergent and controversial broadband emission Stokes-shifted down from the narrow band emission. This paper uncovers the sub- and above-bandgap emission and absorption characteristics of PEA2PbI4 prepared with gap states introduced during single crystal growth. Here, gap states led to coexistent intrinsic and heterostructured electronic frameworks that are selectively accessible with ultraviolet (UV) and infrared (IR) light, respectively, resulting in the phenomenon of photoluminescence (PL) switching from narrowband green to broadband red. Electron-energy dependent cathodoluminescence shows a relative increase in the broadband red PL intensity as the electron penetration depth increases from 30 nm to 2 μm, confirming the heterostructured framework is formed in the bulk of the crystal. Excitation-emission power slope of 2.5 and up-conversion pump transient absorption (TA) spectra suggest that the IR up-conversion excitation with red photoluminescence, peaked at 655 nm, is a multiphoton process occurring in the heterostructured framework through a nonlinear optical response. The energetic pathways toward the dual emission bands are revealed by pump-probe transient absorption spectroscopy, showing energetically broad gap states with high sensitivity to an IR pump are upconverted and subsequently quickly relax from high to low energy levels within 4 ps. Furthermore, the up-conversion red PL demonstrates a linear polarization with magnetic field effects, thus affirming that the band-like heterostructured framework is crystallographically aligned with characteristics of spatially extended charge-transfer states.

Bulk aluminum 7075 alloy strengthened by nano-sized Al-Ni intermetallic particles is synthesized by friction stir processing (FSP). Al 7075 alloy powders mixed with 10 wt% Ni nano powders were used as feedstock. The extensive thermal-mechanical actions by FSP accelerate the reaction and inter-diffusion between Al 7075 powder particles and Ni nano powder particles, resulting in the formation of Al3Ni nano particles, in-situ during FSP, confirmed by scanning electron microscopy and X-ray diffraction. The presence of the Al3Ni nano particles in the Al 7075 matrix increases the micro hardness by 19.0 % and 14.6 %, respectively, under as-processed and T6 aged conditions, compared to the one synthesized by FSP from 100 % 7075 alloy powder. The hardness increment agrees with the estimation from the Orowan strengthening effect of the Al3Ni reinforcement. Furthermore, Al 7075 alloy with in-situ formed Al3Ni shows a tendency of promoting T-Al2Mg3Zn3 and inhibiting eta-MgZn2 precipitation during post synthesis heat treatment between 50 and 500 degrees C. This work suggests the potential of FSP as an effective process to bulk synthesize Al alloys with in-situ formation of Al3Ni nano particles to further enhance the properties.

Spectrally narrow optical resonances can be used to generate slow light, i.e., a large reduction in the group velocity. In a previous work, we developed hybrid 2D semiconductor plasmonic structures, which consist of propagating optical frequency surface-plasmon polaritons interacting with excitons in a semiconductor monolayer. Here, we use coupled exciton-surface plasmon polaritons (E-SPPs) in monolayer WSe 2 to demonstrate slow light with a 1300 fold decrease of the SPP group velocity. Specifically, we use a high resolution two-color laser technique where the nonlinear E-SPP response gives rise to ultra-narrow coherent population oscillation (CPO) resonances, resulting in a group velocity on order of 10 5 m/s. Our work paves the way toward on-chip actively switched delay lines and optical buffers that utilize 2D semiconductors as active elements.

Interlayer excitons (IXs) in 2D semiconductors have long lifetimes and spin-valley coupled physics, with a long-standing goal of single exciton trapping for valleytronic applications. In this work, we use a nano-patterned graphene gate to create an electrostatic IX trap. We measure a unique power-dependent blue-shift of IX energy, where narrow linewidth emission exhibits discrete energy jumps. We attribute these jumps to quantized increases of the number occupancy of IXs within the trap and compare to a theoretical model to assign the lowest energy emission line to single IX recombination.

Al-Ni composite material was fabricated by friction stir process (FSP) using Al 7075 alloy powder mixed with 10 wt% Ni nano powder as feedstock (denoted as ‘10Ni’). The hot-compressed pure Al 7075 (denoted as ‘7075p’) is fabricated with the same process for comparative study. Scanning electron microscopy (SEM), and X-ray diffraction (XRD) indicate the in-situ transformation of most Ni addition to Al 3 Ni particles in the matrix solely by the FSP. The composite ‘10Ni’ presents Vickers hardness of 109.6 HV and 145.2 HV in as-processed (AP) and T6 aged conditions, which achieves 19.0% and 14.6% hardness increment than that of ‘7075p’. ‘10Ni’ shows tendency of promoting T-Al 2 Mg 3 Zn 3 and inhibiting η-MgZn 2 precipitation with respect to ‘7075p’ in XRD tests with ramping temperature (50-500°C). The Orowan strengthening effect of the Al 3 Ni reinforcement is evaluated for the ‘10Ni’ material. This work displays the potential of FSP as a facile and effective tool to process the materials for surface enhancement.

When semiconducting transition metal dichalcogenides heterostructures are stacked the twist angle and lattice mismatch leads to a periodic moiré potential. As the angle between the layers changes, so do the electronic properties. As the angle approaches 0- or 60-degrees interesting characteristics and properties such as modulations in the band edges, flat bands, and confinement are predicted to occur. Here we report scanning tunneling microscopy and spectroscopy measurements on the band gaps and band modulations in MoSe2/WSe2 heterostructures with near 0 degree rotation (R-type) and near 60 degree rotation (H-type). We find a modulation of the band gap for both stacking configurations with a larger modulation for R-type than for H-type as predicted by theory. Furthermore, local density of states images show that electrons are localized differently at the valence band and conduction band edges.

: Interlayer excitons (IXs) in 2D semiconductors have long lifetimes and spin-valley coupled physics, with a long-standing goal of single exciton trapping for valleytronic applications. In this work, we use a nano-patterned graphene gate to create an electrostatic IX trap. We measure a unique power-dependent blue-shift of IX energy, where narrow linewidth emission exhibits discrete energy jumps. We attribute these jumps to quantized increases of the number occupancy of IXs within the trap and compare to a theoretical model to assign the lowest energy emission line to single IX recombination.

When semiconducting transition metal dichalcogenide heterostructures are stacked, the twist angle and lattice mismatch lead to a periodic moiré potential. As the angle between the layers changes, so do the electronic properties. As the angle approaches 0° or 60°, interesting characteristics and properties, such as modulations in the band edges, flat bands, and confinement, are predicted to occur. Here, we report scanning tunneling microscopy and spectroscopy measurements on the bandgaps and band modulations in MoSe2/WSe2 heterostructures with near 0° rotation (R-type) and near 60° rotation (H-type). We find a modulation of the bandgap for both stacking configurations with a larger modulation for R-type than for H-type as predicted by theory. Furthermore, local density of states images show that electrons are localized differently at the valence band and conduction band edges.

Coal is a vital energy resource worldwide, but pollutants and greenhouse gases from its combustion cause environmental problems. To explore the non-combustion approach to use and valorize coal, anthracite and lignite were blended with polyamide 12 (PA 12) through FDM printing in this work and compared in the composites. By adding lignite, Young’s modulus improved with increasing loading to 50 wt% while tensile strength leveled off among the composites, compared to that of PA 12. By contrast, the addition of anthracite decreased the tensile performance at all loadings. Rheology tests and morphology analyses suggested that the interactions between fillers (anthracite and lignite) and PA 12 may cause differences in tensile properties. In addition, the printed lignite composites showed improved thermal conductivity (~ twofold), indicating lignite demonstrates the potential to build functional composites. This work provides a strategy to use lignite in composites by 3D printing for value-added products and reduces the demand for petroleum-based polymers. Our approach diverts lignite from combustion processes and alleviates the negative impact of lignite use on the environment.