Austrian Centre for Electron Microscopy and Nanoanalysis

We prepared rhombohedral and cubic KBiS 2 thin films under mild conditions and demonstrated the formation of oxygen centered radicals along with an excellent charge carrier lifetime upon irradiation.

Solid‐state batteries are attracting considerable attention for their high‐energy density and improved safety over conventional lithium‐ion batteries. Among solid‐state electrolytes, sulfide‐based options like Li 6 PS 5 Cl are especially promising due to their superior ionic conductivity. However, interfacial degradation between sulfide electrolytes and high‐voltage cathodes, such as LiCoO 2 , limits long‐term performance. This study demonstrates that a LiBF 4 ‐derived F‐rich coating on LiCoO 2 , applied by immersing LiCoO 2 particles in a LiBF 4 solution followed by annealing, can significantly enhance performance in Li 6 PS 5 Cl‐based solid‐state batteries. This coating enables stable high‐voltage (4.5 V vs Li + /Li) operation, achieving an initial specific capacity of 153.82 mAh g −1 and 87.1% capacity retention over 300 cycles at 0.5C. The enhanced performance stems from the F‐rich coating, composed of multiple phases including LiF, CoF 2 , Li x BF y O z , and Li x BO y , which effectively suppresses side reactions at the LiCoO 2 |Li 6 PS 5 Cl interface and improves lithium‐ion diffusivity, thereby enabling greater Li capacity utilization. Our findings provide a practical pathway for advancing solid‐state batteries with high‐voltage LiCoO 2 cathodes, offering substantial promise for next‐generation energy storage systems.

Hard metals are in great demand in areas that require high hardness and wear resistance. Tungsten carbide excels in this area, especially with cobalt as a binder phase [1, 2]. For microstructural characterization, choosing an applicable preparation method is the most essential step. Publications concerning WC-Co materials were published by the National Physical Laboratory in Teddington, England, notably by Prof. B. Roebuck, though the influence of preparation methods was not entirely explored. Electron backscatter diffraction (EBSD) is one of the most common characterization techniques for metallurgical investigations. We use common preparation techniques and a few others we developed to analyze and compare the resulting surface quality and their applicability for EBSD [3, 4, 5, 6]. In addition to EBSD, the sample should be compatible with X-ray diffraction (XRD) and/or transmission electron microscopy (TEM) characterization. Our criteria consider EBSD grain indexing in orientation imaging microscopy analysis (OIM) software, changes in microstructure, cobalt leaching/cobalt losses, the size of the characterization area and ease of preparation procedure. We target the distribution of cobalt phases, hexagonal close packing (HCP) and face-centered cubic (FCC) with respect to their magnetic saturation. HCP is stable at room temperature, while FCC forms at temperatures higher than 417 °C [7].

Measuring the atomic-scale surface structure of KTaO3 (KTO) is important and challenging due to its broken translational symmetry. Here, we employed integrated differential phase contrast imaging to resolve the KTO surface at atomic resolution. Through precise measurements of lattice constants, bond lengths, atomic displacements, and strain gradients, we determined the polarization characteristics at the subunit-cell level. Our results reveal a significant increase in lattice constants and strain gradients within the top ∼4 unit cells as the out-of-plane polarization enhances. Electron energy loss spectroscopy further uncovered the electronic origins of surface reconstruction, showing pronounced distortions of the Ta-O octahedra. In combination with density functional theory calculations, we demonstrate that these effects arise from surface-driven orbital reconstruction and Ta-O hybridization. This work offers insights into subunit-cell surface polarization and is expected to provide guidance for surface engineering in functional applications.