I15-Extreme Conditions
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Diamond Proposal Number(s):
[40347]
Open Access
Abstract: We report a comparative high-pressure study of two fluorite-type rare-earth oxides with increasing configurational entropy, (CePr)O2–δ and (CePrLa)O2–δ. Synchrotron-based powder X-ray diffraction and Raman spectroscopy were carried out up to 30 and 20 GPa, respectively. Both compounds retain the cubic fluorite structure throughout the pressure range explored, although an anomaly is observed between 9 and 16 GPa, characterized by a compressibility plateau and changes in vibrational modes. This behavior is attributed to local lattice distortions and a progressive bond angle bending rather than abrupt phase transitions. In (CePrLa)O2−δ, the onset of amorphization is observed above 22 GPa, highlighting its reduced structural stability. The bulk modulus of both systems shows a slight decrease after the onset of the anomaly, suggesting subtle lattice softening. Raman spectroscopy reveals suppression of the F2g mode intensity with increasing cationic disorder, and under compression, partial reordering is evidenced by an increase in the RE–O mode intensity. Our results highlight the complex interplay between configurational entropy, cation size, and pressure in determining the structural stability and vibrational properties of rare-earth high-entropy oxides and provide insight into the mechanisms governing their resilience and local disorder under extreme conditions.
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Dec 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[36397]
Abstract: Despite remaining enigmatic, strong hydrogen bonding provides an advanced design handle for tailoring the properties of functional materials. Here, 3R–(H/D)RhO2 delafossites (prepared by ion exchange of Na+ from NaRhO2) contain H/D in linear coordination with O, linking RhIIIO2 layers. Bragg and real-space X-ray and neutron scattering analysis, vibrational and solid-state NMR spectroscopy, and density functional theory (DFT)–based electronic structure calculations have been employed to understand the nature of the hydrogen bonding. Despite short distances between H/D and the two O to which they are bonded, a clear double-minimum corresponding to a shorter and longer (H/D)–O distance is established. The triangular lattices formed by H/D appear to display ice-like disorder, corroborated by low-temperature heat capacity measurements.
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Nov 2025
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E02-JEM ARM 300CF
I11-High Resolution Powder Diffraction
I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[40887]
Open Access
Abstract: Owing to their vast chemical and structural flexibility, layered double hydroxides (LDHs) are among some of the most promising materials for many catalytic applications. Thermal decomposition below 700 °C leads to the formation of a complex semiamorphous mixed metal oxide (LDO). In this study, the product of calcination of aqueous miscible organic solvent-treated AMO-[Mg0.70Al0.30(OH)2](CO3)0.15·yH2O·zEtOH at 600 °C (AMO-Mg2.33Al LDO) has been investigated using a synergistic combination of high-resolution synchrotron X-ray and neutron scattering techniques, as well as high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), solid-state NMR (ssNMR), and thermogravimetric analysis coupled with mass spectrometry (TGA-MS). The local and extended structure of AMO-Mg2.33Al LDO has been modeled by reciprocal and real space X-ray and neutron scattering analyses and is consistent with a modified rock salt structure consisting of octahedrally coordinated layers containing a small number of vacancies and the tetrahedrally coordinated Al3+ sites in contrast to previous reports.
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Nov 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[34800]
Open Access
Abstract: Layered crystal structures are commonly found across organic and inorganic material systems. When in-plane atomic arrangement remains (nearly) identical, a stacking variation of these layers may result in twinning, planar disorder, or polytypes, a form of polymorphism derived from altering stacking sequences. In this work, we use multi-dimensional electron diffraction (ED) modalities to explore the microstructure of xanthine, an archetypal purine base with a layered crystal structure. Firstly, we identify and characterise the twin operator relating domains of Form I xanthine. We then solve the structure of a new xanthine polymorph, revealing that it is a polytype of Form I. Finally, interfaces between twin and polytype domains are visualised, whilst streaking in the diffraction patterns reveals the presence of planar disorder. Given these observations in the xanthine system, this work suggests that disorder on the nanoscale may be a commonly occurring phenomenon in layered organic molecular crystals.
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Nov 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[38725]
Open Access
Abstract: The Cr-Mo-Si-Ni-Al alloy system was investigated with the goal of combining recent advances in the two-phase Cr-Mo-Si system [(Cr,Mo)-A2 matrix + (Cr,Mo)3Si-A15 precipitates], with the approach of strengthening the Cr matrix with the low misfit precipitate NiAl (B2). The role of Mo and Si in the system was investigated in alloys that were arc-melted, annealed, and characterized for microstructure, hardness, fracture toughness, and compressive strength at various temperatures (21–1000 °C). Unlike the A15 phase, the B2 phase does not reduce the fracture toughness of the Cr solid solution matrix. The yield stress of the A2–B2 system is comparable to that of the A2–A15 system, but retains its strength up to higher temperatures (tested up to 1000 °C). The addition of Ni and Al to the Cr-Mo-Si system shifts the stability regime of the σ phase in the system to lower Mo and Si contents and lower temperatures. Since Ni shows high solubility in the σ phase, reducing the Ni/Al ratio reduces the amount of the σ phase. The implementation of NiAl precipitates to the Mo- and Si-strengthened Cr matrix has a beneficial effect on the high-temperature strength and low-temperature fracture toughness of the Cr-based alloys.
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Nov 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[32708]
Open Access
Abstract: BCC superalloys are a promising class of high-temperature materials with a wide range of lattice misfit values, ranging from near-zero to ∼8 %. Analogous to nickel superalloys, lattice misfit combined with elastic anisotropy dictates precipitate morphology (spherical, cuboidal, plate/needle-like), coarsening kinetics, strengthening mechanisms, and microstructure evolution, making misfit control critical for tailoring microstructural stability and creep resistance. However, misfit characterisation, especially at high temperatures, is still in its infancy to establish its links with mechanical properties. This perspective emphasises three aspects of BCC superalloys: representative misfit-driven microstructures and temperature-dependent misfit evolution, state-of-the-art diffraction techniques for high-temperature misfit quantification, and machine learning frameworks to accelerate alloy design involving misfit. By consolidating diverse misfit data and advanced characterisation/modelling strategies, we outline strategies to bridge computational and experimental gaps, advocating for physics-informed models and high-throughput techniques to design next-generation BCC superalloys and motivate systematic studies on the misfit-property relationship in this nascent material class.
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Oct 2025
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
B18-Core EXAFS
E02-JEM ARM 300CF
I11-High Resolution Powder Diffraction
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Mengqi
Duan
,
Shuai
Guo
,
Wentian
Niu
,
Hangjuan
Ren
,
Thomas
Dittrich
,
Dongpei
Ye
,
Lucy
Saunders
,
Sarah
Day
,
Veronica
Celorrio
,
Diego
Gianolio
,
Peixi
Cong
,
Robert S.
Weatherup
,
Robert
Taylor
,
Songhua
Cai
,
Yiyang
Li
,
Shik Chi Edman
Tsang
Diamond Proposal Number(s):
[35749, 35750, 35961, 37117]
Open Access
Abstract: Two-dimensional layered perovskite oxides have emerged as promising photocatalysts for solar-driven hydrogen evolution. Although doping has been widely employed to enhance photocatalytic performance, its role in modulating the electronic structure and the local chemical environment of these materials remains poorly understood. Here in this study, we investigate the codoping of Rh and La into exfoliated nanosheets of the Dion–Jacobson perovskite KCa2Nb3O10 to enhance photocatalytic hydrogen evolution reaction (HER) activity. A substantial increase in H2 evolution rate, from 12.3 to 69.0 μmol h–1, was achieved at an optimal doping level of 0.2 wt % Rh and 1.3 wt % La. Comprehensive structural and spectroscopic analyses, including synchrotron techniques and high-resolution microscopy, revealed that Rh3+ substitutes Nb5+ to introduce shallow 4d acceptor states that mediate charge separation, while La3+ substitutes Ca2+, compensates for aliovalent charge imbalance, and modulates local lattice distortions and oxygen vacancy formation. This codoping strategy enhances charge carrier lifetime and separation efficiency through a trap-mediated mechanism. The observed volcano-shaped activity trend highlights a narrow compositional window, where electronic and structural factors are optimally balanced. These findings establish a mechanistic foundation for defect engineering in layered perovskites and offer a pathway for the rational design of photocatalysts.
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Oct 2025
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I11-High Resolution Powder Diffraction
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Open Access
Abstract: The first reported phase in the Y2O3–NiO–TiO2 chemical space, the Y2NiTiO6 perovskite undergoes a temperature-induced order–disorder transition. Above ∼1700 K, it adopts the structure of a disordered CaTiO3-type orthorhombic perovskite with a = 5.26939(2), b = 5.60367(2), and c = 7.58137(3) Å, with the B site uniformly occupied by 0.5Ni+0.5Ti. Below this temperature, Y2NiTiO6 adopts rock-salt ordering of the transition metals in a monoclinic unit cell (a = 5.26695(2), b = 5.60164(2), c = 7.57493(2) Å, β = 90.4940(2)°) with 0.9/0.1 ordering of the B site. Ordering of Ni and Ti changes the magnetic properties from spin-glass behavior in the orthorhombic phase to antiferromagnetic order (TN = 17 K) for the monoclinic phase, while the optical properties of both phases remain unchanged across the transition.
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Oct 2025
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B18-Core EXAFS
I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[34632, 31578]
Open Access
Abstract: Biomass conversion involves transforming sustainable feedstocks into valuable intermediates for the chemical industry. A key biomass-derived platform molecule, 5-hydroxymethylfurfural (HMF), can be converted into various intermediates, including 2,5-diformylfuran (DFF), which has several industrial applications due to its versatile chemical reactivity. Herein, Cu loaded MOF-808, with three different Cu loadings, were synthesised and tested as catalysts for the liquid phase selective oxidation of HMF to DFF with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) were performed to assess the speciation of Cu, with the development of a structure model of MOF-808(Cu3). The structural analysis reveals that single square planar Cu(II) sites are located near the Zr6 cluster and are bonded by coordinating to oxygen atoms of capping MeOH and H2O ligands. Amongst the synthesised catalysts, MOF-808(Cu3) exhibited the highest catalytic activity after 12 h, achieving a high HMF conversion (95.5 ± 2.7%) and DFF yield (78.9 ± 1.3%) at 30 °C. The nature of the catalytic reaction is heterogeneous as the yield of DFF decreases after the removal of the solid catalyst. The demonstration of catalytic activity with high selectivity under near ambient conditions advances the application of porous metal–organic framework-based catalysts for selective liquid phase oxidations.
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Oct 2025
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I11-High Resolution Powder Diffraction
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Diamond Proposal Number(s):
[40562]
Open Access
Abstract: The paper presents the study of phase and structural behavior of pseudoternary compound (Ga1-x-yInxAly)2O3 with focus on the compositional cross-section where the x/y ratio is a fixed at 0.31/0.69. This specific ratio ensures that the average cation radius, equal to that of Ga3+ ions, remains unchanged. Through the combination of experimental XRD studies and DFT calculations, the stability region of the monoclinic phase within the Ga2O3–Al2O3–In2O3 ternary system was established. Detailed analysis of the crystal lattice parameters and unit cell volume of the monoclinic structure was carried out across a wide range of compositions. An empirical relationship was derived linking the monoclinic lattice parameters to the average ionic radius of the cations (Ga3+, Al3+, In3+) enabling prediction of lattice parameters in monoclinic (Ga1-x-yInxAly)2O3 solely from chemical composition. The experimental crystal structure studies and the electronic structure calculations suggest that in the monoclinic (Ga1-x-yInxAly)2O3 structure the tetrahedral positions of Ga1 atoms are preferentially occupied by Ga3+ and Al3+ cations, while the octahedral Ga2 sites accommodate a mixture of Ga3+, Al3+ and In3+ cations. Additionally, the presence of unidentified phase(s) was confirmed in the central region of the Ga2O3–Al2O3–In2O3 triangle. Comparison of the calculated optical absorption spectra and the Tauc-plots derived from the diffuse reflectance spectra indicate that the monoclinic (Ga1−x−yInxAly)2O3 compounds have a direct band gap.
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Oct 2025
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