The ID28 beamline (ESRF) hosts the only inelastic x-ray scattering spectrometer in Europe and is devoted to the study of phonons. As part of a rich portfolio of user activities high-pressure research represents a vital segment of the beamline's research portfolio, constituting approximately 30% of allocated beamtime, with users benefiting from both the extreme brightness and tight focusing capabilities of the European synchrotron. Here we present the current status of lattice dynamics studies under (quasi)hydrostatic pressure which have become close-to-routine measurements, detail a selection of example studies and briefly discuss potential future advances.

Although the principal physical behaviour of a material is inherently connected to its fundamental crystal structure, the behaviours observed in the real-world are often driven by the microstructure, which for many polycrystalline materials, equates to the size and shape of the constituent crystal grains. Here we highlight a cutting edge synthesis route to the controlled engineering of grain structures in thin films and the simplification of associated 3-dimensional problems to less complex 2D ones. This has been applied to the actinide ceramic, uranium dioxide, to replicate structures typical in nuclear fission fuel pellets, in order to investigate the oxidation and subsequent transformation of cubic UO2 to orthorhombic U3O8. This article shows how this synthesis approach could be utilised to investigate a range of phenomena, affected by grain morphology, and highlights some unusual results in the oxidation behaviour of UO2, regarding the phase transition to U3O8.

The observation of unexpected polarisation textures such as vortices, skyrmions and merons in various oxide heterostructures has challenged the widely accepted picture of ferroelectric domain walls as being Ising-like. Bloch components in the 180 domain walls of PbTiO3 have recently been reported in PbTiO3/SrTiO3 superlattices and linked to domain wall chirality. While this opens exciting perspectives, the ubiquitous nature of this Bloch component remains to be further explored. In this work, we present a comprehensive investigation of domain walls in PbTiO3/SrTiO3 superlattices, involving a combination of first- and second-principles calculations, phase-field simulations, diffuse scattering calculations, and synchrotron based diffuse x-ray scattering. Our theoretical calculations highlight that the previously predicted Bloch polarisation in the 180 domain walls in PbTiO3/SrTiO3 superlattices might be more sensitive to the boundary conditions than initially thought and is not always expected to appear. Employing diffuse scattering calculations for larger systems we develop a method to probe the complex structure of domain walls in these superlattices via diffuse x-ray scattering measurements. Through this approach, we investigate depolarization-driven ferroelectric polarization rotation at the domain walls. Our experimental findings, consistent with our theoretical predictions for realistic domain periods, do not reveal any signatures of a Bloch component in the centres of the 180 domain walls of PbTiO3/SrTiO3 superlattices, suggesting that the precise nature of domain walls in the ultrathin PbTiO3 layers is more intricate than previously thought and deserves further attention.

The observation of unexpected polarization textures such as vortices, skyrmions, and merons in The observation of unexpected polarization textures such as vortices, skyrmions, and merons in various oxide heterostructures has challenged the widely accepted picture of ferroelectric domain various oxide heterostructures has challenged the widely accepted picture of ferroelectric domain walls as being Ising-like. Bloch components in the 180 degrees domain walls of PbTiO3 have recently been walls as being Ising-like. Bloch components in the 180 degrees domain walls of PbTiO3 have recently been reported in PbTiO3/SrTiO3 superlattices and linked to domain wall chirality. While this opens reported in PbTiO3/SrTiO3 superlattices and linked to domain wall chirality. While this opens exciting perspectives, the ubiquity of this Bloch component remains to be further explored. In this exciting perspectives, the ubiquity of this Bloch component remains to be further explored. In this work, we present a comprehensive investigation of domain walls in PbTiO3/SrTiO3 superlattices, work, we present a comprehensive investigation of domain walls in PbTiO3/SrTiO3 superlattices, involving a combination of first- and second-principles calculations, phase-field simulations, diffuse involving a combination of first- and second-principles calculations, phase-field simulations, diffuse scattering calculations, and synchrotron-based diffuse x-ray scattering. Our theoretical calculations scattering calculations, and synchrotron-based diffuse x-ray scattering. Our theoretical calculations highlight that the previously predicted Bloch polarization in the 180 degrees domain walls in PbTiO3/SrTiO3 highlight that the previously predicted Bloch polarization in the 180 degrees domain walls in PbTiO3/SrTiO3 superlattices might be more sensitive to the boundary conditions than initially thought and is not superlattices might be more sensitive to the boundary conditions than initially thought and is not always expected to appear. Employing diffuse scattering calculations for larger systems, we develop always expected to appear. Employing diffuse scattering calculations for larger systems, we develop a method to probe the complex structure of domain walls in these superlattices via diffuse x-ray a method to probe the complex structure of domain walls in these superlattices via diffuse x-ray scattering measurements. Through this approach, we investigate depolarization-driven ferroelectric scattering measurements. Through this approach, we investigate depolarization-driven ferroelectric polarization rotation at the domain walls. Our experimental findings, consistent with our theoretical polarization rotation at the domain walls. Our experimental findings, consistent with our theoretical predictions for realistic domain periods, do not reveal any signatures of a Bloch component in the predictions for realistic domain periods, do not reveal any signatures of a Bloch component in the centers of the 180 degrees domain walls of PbTiO3/SrTiO3 superlattices, suggesting that the precise nature centers of the 180 degrees domain walls of PbTiO3/SrTiO3 superlattices, suggesting that the precise nature of domain walls in the ultrathin PbTiO3 layers is more intricate than previously thought and deserves of domain walls in the ultrathin PbTiO3 layers is more intricate than previously thought and deserves further attention. further attention.

Despite many years of research, the full complexity of the electron-lattice interactions in ${\mathrm{UO}}_{2}$ is not fully understood. We present x-ray inelastic scattering at low temperature showing that the interaction between electronic degrees of freedom and transverse acoustic phonons is strong only along the reciprocal space direction [100]. The anisotropy is reflected in the phonon-linewidth broadening, which persists also well above the N\'eel temperature. This intrinsic effect infers an anisotropy in the thermal conductivity, which has been observed, but which is formally forbidden in a cubic material. We have no model capable of connecting our experimental observations with the low thermal conductivity of ${\mathrm{UO}}_{2}$ below room temperature.

Understanding the role of disorder, and the correlations that exist within it, is one of the defining challenges in contemporary materials science. However, there are few material systems, devoid of other complex interactions, that can be used to systematically study the effects of crystallographic conflict on correlated disorder. Here, we report extensive diffuse x-ray scattering studies on the epitaxially stabilized alloy U1-xMox, showing that a new form of intrinsically tuneable correlated disorder arises from a mismatch between the preferred symmetry of a crystallographic basis and the lattice upon which it is arranged. Furthermore, combining grazing incidence inelastic x-ray scattering and state-of-the-art ab initio molecular dynamics simulations, we discover strong disorder-phonon coupling. This breaks global symmetry and dramatically suppresses phonon lifetimes compared to alloying alone, providing an additional design strategy for phonon engineering. These findings have implications wherever crystallographic conflict can be accommodated, and they may be exploited in the development of future functional materials.

In defining the corrosion control requirements for DEMO, the impact of the mixed Eurofer-97/AISI 316 steel system and plant specific effects should be considered-throughout, in particular, the effect of the intense magnetic fields present. A substantial amount of data related to corrosion resistance of structural materials is available for industrial applications in fission, but applies to different materials and neutronic conditions. Experimental work is being carried out under the DEMO Breeding Blanket Project of the EUROfusion programme, which will further develop the understanding of irradiation effects. However, there is very limited information regarding magnetic field-assisted corrosion under conditions relevant for the fusion environment readily available in the literature. This work reviews current knowledge and progress in establishing the possible influence of the intense magnetic field on corrosion behaviour of the main structural material, Eurofer-97, in the breeding blanket. To support the relevance of this problem statement, preliminary corrosion experimental results of Eurofer-97 coupons, obtained by using a simple apparatus that allows exposure to a magnetic field intensity of 0.88 T and temperatures up to 80 degrees C in water at atmospheric pressure, are presented as an initial qualitative investigation of possible magnetic field related effects.