Controlling the anionic stoichiometry and distribution of perovskite cobaltites presents a powerful method for tailoring the magnetic and electronic properties for magneto-ionic applications. Nevertheless, the influence of nanoscale morphology, including phase separation and defects in cobaltite heterostructures, remains largely unexplored. We used x-ray nanodiffraction to directly image the nanoscale topotactic phase transformation in La1−xSrxCoO3 (LSCO) heterostructures capped with a reactive aluminum (Al) layer (i.e., oxygen “getter”) of varying thicknesses (0.5, 3, and 7 nm). Nanodiffraction images reveal the formation of highly elongated BM filaments extending over mesoscopic lengths (>67 μm), indicating a strong tendency toward oxygen vacancy ordering in both P and BM phases in all heterostructures. Local strain and strain gradient analysis shows a strong correlation between the depletion of the P phase and strain gradients. Our measurements suggest that elongation of the BM filaments is the predominant mechanism for topotactic transformation in LSCO/Al heterostructures, preferred over coarsening, branching, and fractal growth. Our study provides a detailed nanoscale analysis of ionically driven phase transitions in LSCO/Al heterostructures, which is crucial for tailoring the functional properties of cobaltites for magneto-ionic devices.

A fundamental understanding of network structure and associated atomic-scale mechanisms in silicate glasses under dynamic compression is crucial for explaining several phenomena including, planetary formation, core-mantle boundary dynamics, and the design of high-performance glasses for military and aerospace application. Although pure silica has been extensively studied, the behavior of modified silicate glasses is often extrapolated from pure silica, with direct structural evidence remaining limited. We directly probed nanosecond-scale structural dynamics in silicate glasses containing network-forming cations (borosilicate glass) and network-modifying cations (soda-lime glass) using time-resolved X-ray diffraction and laser-driven shock compression. Distinct polymorphic behavior, strongly dependent on the network structure, was observed between 40 and 65 GPa. Borosilicate glass undergoes polymorphic phase transitions with crystal symmetry strongly dependent on the pressure, whereas soda-lime glass exhibits changes in coordination number without a corresponding change in the global symmetry. Above 65 GPa, both glasses respond similarly, exhibiting increasing densification and structural disorder, ultimately leading to melting.

Composition and network structure of doped silicate glasses can strongly dictate the material properties including dynamic behavior in extreme conditions. The fundamental understanding of the role of network structure and related atomic-scale mechanisms are crucial for a wide range of phenomena including planetary interiors and formation, processes underpinning core-mantle boundary dynamics, and high-performance glasses for military and aerospace applications. While the high pressure-temperature phase diagram of pure silica has been widely studied, the behavior of compositionally modified silicate glasses has been extrapolated based on pure silica, and direct evidence based on structural measurements has been lacking. Using time-resolved x-ray diffraction and laserdriven shock compression, we directly resolved nanosecond structural dynamics in silicate glasses doped with network forming cations (borosilicate glass) and network modifying cations (soda-lime glass). From 40 to 60 GPa, distinct polymorphic behavior strongly dependent on network structure is observed. Borosilicate glass undergoes polymorphic phase transitions with crystal symmetry strongly dependent on the pressure, while soda-lime glass undergoes modification of coordination number but no change in global crystal symmetry. Above 70 GPa, the responses of both glasses are independent of the network structure with a resultant diaplectic (shocked-produced densified) glass phase. These results establish novel and complex phase diagram of doped silicate glasses from 40 to 312 GPa.

Shock experiments give a unique insight into the behavior of matter subjected to extremely high pressures and temperatures. Understanding the behavior of materials under such extreme conditions is key to modeling material failure and deformation dynamics under impact. While studies on pure silica are extensive, the shock behavior of other commercial silicates that contain additional oxides has not been systematically investigated. To better understand the role of composition in the dynamic behavior of silicates, we performed laser-driven dynamic compression experiments on soda-lime glass (SLG) up to 315 GPa. Using the accurate pulse shaping offered by the long pulse laser system at the Matter in Extreme Conditions end-station at the Linac Coherent Light Source, SLG was shock compressed along the Hugoniot to multiple pressure-temperature points. Velocity Interferometer System for Any Reflector was used to measure the velocity and determine the pressure inside the SLG. The Us–up relationship obtained agrees well with the previous parallel plate impact studies. Within the error bars, no transformation to the crystalline phase was observed up to 70 GPa, which is in contrast to the behavior of pure silica under shock compression. Our studies show that the glass composition strongly influences the shock compression behavior of the silicate glasses.

Photoinduced structural dynamics of rare-earth nickelate thin films, NdNiO3 and SmNiO3, grown on (001) oriented SrTiO3 were studied using time-resolved x-ray diffraction. The evolution of the (002) Bragg peak was tracked following laser excitation. The recovery pathways were found to be strongly dependent on laser fluence for NdNiO3 and distinct for the two rare-earth nickelates. The recovery of the (002) peak shifts was modeled using a one-dimensional thermal diffusion model which showed that the recovery processes are nonthermal at high fluences. For NdNiO3, the timescales for the recovery of the (002) peak shift were found to be closely related to Ni magnetism recovery, potentially indicating magnetostructural coupling. Moreover, the evolution of integrated intensity and full width at half maximum points towards the presence of a structural phase separation during recovery. Our studies highlight structural recovery pathways in nickelates by comparing the distinct responses of the photoinduced metal-insulator transition in NdNiO3 and SmNiO3.