Tern�re Halogenide vom Typ A3MX6. IV. [1]. Tern�re Halogenide des Scandiums mit Natrium, Na3ScX6 (X = F, Cl, Br): Synthese, Strukturen, Ionenleitf�higkeit

Re-investigating the structure-property relationship of the solid electrolytes Li 3-x In1-x Zr x Cl6 and the impact of In-Zr(iv) substitution

Chloride-based solid electrolytes are considered interesting candidates for catholytes in all-solid-state batteries due to their high electrochemical stability, which allows the use of high-voltage cathodes without protective coatings. Aliovalent Zr(iv) substitution is a widely applicable strategy to increase the ionic conductivity of Li₃M(iii)Cl₆ solid electrolytes. In this study, we investigate how Zr(iv) substitution affects the structure and ion conduction in Li_3-x In_1-x Zr _x Cl₆ (0 ≤ x ≤ 0.5). Rietveld refinement using both X-ray and neutron diffraction is used to make a structural model based on two sets of scattering contrasts. AC-impedance measurements and solid-state NMR relaxometry measurements at multiple Larmor frequencies are used to study the Li-ion dynamics. In this manner the diffusion mechanism and its correlation with the structure are explored and compared to previous studies, advancing the understanding of these complex and difficult to characterize materials. It is found that the diffusion in Li₃InCl₆ is most likely anisotropic considering the crystal structure and two distinct jump processes found by solid-state NMR. Zr-substitution improves ionic conductivity by tuning the charge carrier concentration, accompanied by small changes in the crystal structure which affect ion transport on short timescales, likely reducing the anisotropy.

Combined Approach for the Structural Characterization of Alkali Fluoroscandates: Solid-State NMR, Powder X-ray Diffraction, and Density Functional Theory Calculations

The structures of several fluoroscandate compounds are presented here using a characterization approach combining powder X-ray diffraction and solid-state NMR. The structure of K₅Sc₃F₁₄ was fully determined from Rietveld refinement performed on powder X-ray diffraction data. Moreover, the local structures of NaScF₄, Li₃ScF₆, KSc₂F₇, and Na₃ScF₆ compounds were studied in detail from solid-state ¹⁹F and ⁴⁵Sc NMR experiments. The ⁴⁵Sc chemical shift ranges for six- and seven-coordinated scandium environments were defined. The ¹⁹F chemical shift ranges for bridging and terminal fluorine atoms were also determined. First-principles calculations of the ¹⁹F and ⁴⁵Sc NMR parameters were carried out using plane-wave basis sets and periodic boundary conditions (CASTEP), and the results were compared with the experimental data. A good agreement between the calculated shielding constants and experimental chemical shifts was obtained. This demonstrates the good potential of computational methods in spectroscopic assignments of solid-state ⁴⁵Sc NMR spectroscopy.

Cs3ScCl6

Crystals of tricaesium scandium(III) hexa­chloride were obtained as a side product from the reaction of U, SnCl₂, Sc, and S in a CsCl flux at 1073 K. Cs₃ScCl₆ crystallizes in the Rb₃YCl₆ structure type. The asymmetric unit comprises three Cs sites, two Sc sites, and six Cl sites, all of which have site symmetry 1, except for the two Sc sites that have site symmetries of 2 and -1, respectively. The structure is composed of isolated [ScCl₆]³⁻ octa­hedra that are surrounded by Cs⁺ cations. Two Cs⁺ cations have inter­actions with eight Cl⁻ anions, while the third has inter­actions with ten Cl⁻ anions.