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The results of high-throughput screening of the inorganic crystal structure database for new promising Ca2+-, Mg2+-, Zn2+- and Al3+-ion conducting ternary and quaternary sulfides, selenides, and tellurides are presented (∼1500 compounds). A geometrical-topological approach based on the Voronoi partition was initially used and yielded 104 compounds, which were unknown as conductors with possible cation migration. All compounds were passed through the bond valence site energy analysis to determine the migration energy Em. Furthermore, we established the logarithmic dependencies of Em on the geometrical parameters of the migration pathways. As a result, 16 out of 104 structures were filtered out as promising conductors. Finally, density functional theory simulations yielded the 11 most prospective compounds with Em < 1.0 eV. Among them, we found a novel class of ionic conductors with the La3CuSiS7 structure, for which ab initio molecular dynamic calculations were performed, revealing diffusion coefficients of ∼10−7 cm2 s−1 and ionic conductivity of ∼10−2 S cm−1 at 300 K. [ABSTRACT FROM AUTHOR]

This review reports on hybrid sol-gel coatings used for radiation protective purposes. The different types of electromagnetic radiation are usually distinguished by their wavelength, frequency or photon energy. There is a broad range of types of radiation that humans, materials or electric devices are exposed to, starting from radio waves, microwaves, infrared radiation, visible light, UV light, X-ray and gamma-ray radiation. Gamma-ray radiation is thus at the end of the electromagnetic spectrum with smallest wavelengths, highest frequencies and highest photon energies. Protection against radiation make sense, as it can pose health risks or interfere with technical and electronic equipment for example. Radiation protection can be realized by materials that are able to absorb or reflect the radiation, which leads to a considerable reduction in radiation transmission. These radiation protection materials are specific to different types of radiation or spectral widths, e.g., a material with excellent protective properties against UV light is not automatically suitable for protection against infrared light. The main aim of this review article is to report, what types of hybrid sol-gel materials can be used to provide ideal protection against a specific category of radiation. Additional to the broad view on all types of radiations, focusing in particular on materials exhibiting UV protective properties. Highlights: Full overview on hybrid sol–gel materials for radiation protection. View a fundamental issue of radiation protection. Categorization of special sol–gel materials for protection against specific type of radiation. Discussion of relation of UV-protective properties and coloration of materials. [ABSTRACT FROM AUTHOR]

It is well known that LiMO3 crystals contain a natural hydrogen defect, which binds to oxygen and forms OH− defects. Since the shape of the corresponding absorption band varies strongly depending on the crystal stoichiometry, we can use it to elucidate the existence of different hydrogen occupation sites and the associated chemical environment. For this purpose, FT-IR and Raman spectra of the OH− stretching vibration are measured on a set of near-stoichiometric and congruent LiNbO3 and LiTaO3 crystals. Density functional theory and bond valence energy landscape calculations lead to the same result that ideal stoichiometric LiMO3 structures feature two stable hydrogen sites. The two configurations are located on the O–O connection line between two oxygen planes forming a regularly empty octahedron. In contrast to the theoretical calculations, it can be concluded from the experimental FT-IR spectra of near-stoichiometric and congruent material that the OH− defect is almost completely located within the O–O plane perpendicular to the crystallographic c axis. We will show that intrinsic and extrinsic defects are responsible for this positioning of the hydrogen in the O–O plane. The extrinsic defects are paramagnetic impurities decorated with hydrogen. They are responsible for the narrow and dominant sub-band component at ∼3460 cm−1 in near-stoichiometric crystals. The congruent materials have a high intrinsic defect cluster density and especially lithium vacancies are preferentially decorated by hydrogen. These defect sites are assigned to the other sub-band components found in congruent LiMO3 crystals. [ABSTRACT FROM AUTHOR]

Hydrogen incorporation during crystal growth or other treatment has attracted research interest for a long time, but the diffusion paths and the role of additional defect sites within the lithium metal oxides (LiMO3 with M = Nb, and Ta) are still not fully understood. We investigated the hydrogen diffusion by crystal orientation- and light polarization-resolved FT-IR spectroscopy. The OH− stretching vibration is modified by the out- and in-diffusion of hydrogen using appropriate temperature and atmosphere conditions. An isotropic out- and in-diffusion in the congruent as-grown materials was observed. For C-LiNbO3 a higher diffusion rate and a lower activation energy than in C-LiTaO3 were found. In comparison to C-LiTaO3, a possible reason could be the Ta interstitial defect cluster, which limits the diffusion through the empty octahedral sites. The in-diffusion coefficients of reduced crystals are almost two orders of magnitude higher compared to those of the as-grown materials. Obviously, the hydrogen diffusion is promoted by the presence of oxygen and lithium vacancies. Since the defect sites are decorated with hydrogen, the hydrogen saturation concentration depends on the defect concentration. Finally, the same diffusion rate is observed for reduced LiTaO3 and LiNbO3. Consequently, vacancy formation is lifting the diffusion blocking by Ta interstitial defects. [ABSTRACT FROM AUTHOR]

REMo2B5 (RE = Ce, Pr, Nd) and CeW2B5 have been synthesized by arc melting with further annealing at 1300 °C. CeMo2B5 crystallizes in a new structure type with space group Pnma, a = 11.0298(2) Å, b = 3.12080(5) Å, c = 9.9594(2) Å, Z = 4. Its structural arrangement reveals puckered [B6]‐hexagonal rings, trigonal‐prismatic‐ and empty pyramidal‐tetrahedral‐slabs. The structure can be related to the derivatives of AlB2 and CrB prototypes. The boron atoms form a two‐dimensional network of corrugated ribbons, each composed of four edge‐linked [B6] rings infinitely extending along the b‐axis. CeMo2B5 is a Pauli paramagnet. Electrical transport measurements together with the calculated density of states at the Fermi level of 3.81 states eV–1 f.u.–1 indicate CeMo2B5 to be a typical metallic system. Electronic structure calculations reveal significant hybridization of Ce 4f5d states with Mo 4d states. The chemical bonding scenario is dominated by chains of [Ce2Mo2] clusters with multi‐center bonds. These clusters are connected via metallic Mo–Mo bonds. This metal‐framework, in turn, is stabilized by bonding interactions with the boron ribbons to which it donates electrons. [ABSTRACT FROM AUTHOR]

Finding inorganic materials with significant Al ion mobility could push the development of alternative rechargeable batteries, as they could potentially serve as solid electrolytes or intercalation cathodes. While for single‐ and double‐charged ions numerous solid electrolytes are known, the situation is rather unclear and only sparingly researched for ions with a charge higher than two. To assist in the systematic analysis, compounds described in literature as solid electrolytes or intercalation materials for Al3+, as well as some materials generally known for high mobilities for multivalent ions, are critically reviewed and analyzed by the bond‐valence energy landscape approach. For this purpose a thorough list of investigated cathode materials for rechargeable Al batteries is provided first. While it is demonstrated that solid electrolytes for Al3+ cannot be unequivocally identified in literature yet, the analysis of the intercalation cathodes reveals promising structural motifs for comparatively fast Al diffusion, which can be used for the analysis, comparison and design of new promising materials. Furthermore, chances and limits of the bond‐valence energy analysis for high‐valent battery materials are exemplarily shown. Thus, this work aims at encouraging more theoretical and experimental work on Al battery materials and provides guidelines for doing so. [ABSTRACT FROM AUTHOR]

Abstract: The time‐resolved oxygen exchange rate of strontium titanate (SrTiO3) single crystals is studied by means of oxygen solid electrolyte coulometry (OSEC) and compared to model calculations. Experiments are performed on pure, ion implanted (Ni, Ag, O and N ions) and partially covered crystals with silver layer. In this work, a theoretical model is used, which is based on defect chemistry under equilibrium conditions. It is applied as a fit in order to determine the effective rate constants and activation energy of the oxygen exchange reaction on the crystal surface. OSEC is used for the first time to characterize kinetic parameters of oxygen exchange on single crystalline surfaces. Transmission electron microscopy and sputter X‐ray photoelectron spectroscopy are performed to determine structural and chemical changes after ion implantation. [ABSTRACT FROM AUTHOR]