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The novel composition – TiFe1.3Os3.9B2.8 – is the first quaternary phase of the NbRuB structure type. The layer‐like structure consists of boron (mixed with 8 % Fe) dumbbells in the same layer as osmium atoms, some sites with mixed occupancies. The second layer has isolated boron, osmium/titanium (51 % Os) and iron atoms. The presence of iron enables the study of magnetism as Fe‐chains are present, with intra‐ and interchain distances of 3.02 Å and 5.76 Å, respectively. Density functional theory (DFT) predicts magnetic ordering to be likely with the antiferromagnetic ground state only 13 meV more favorable than the ferromagnetic state. This discovery opens the possibilities of studying various quaternary compositions in the superconducting NbRuB structure type. [ABSTRACT FROM AUTHOR]

The novel composition – TiFe1.3Os3.9B2.8 – is the first quaternary phase of the NbRuB structure type. The layer‐like structure consists of boron (mixed with 8 % Fe) dumbbells in the same layer as osmium atoms, some sites with mixed occupancies. The second layer has isolated boron, osmium/titanium (51 % Os) and iron atoms. The presence of iron enables the study of magnetism as Fe‐chains are present, with intra‐ and interchain distances of 3.02 Å and 5.76 Å, respectively. Density functional theory (DFT) predicts magnetic ordering to be likely with the antiferromagnetic ground state only 13 meV more favorable than the ferromagnetic state. This discovery opens the possibilities of studying various quaternary compositions in the superconducting NbRuB structure type. [ABSTRACT FROM AUTHOR]

Garnet-based Li7La3Zr2O12 (LLZO) is considered one of the most promising oxide-ceramic solid electrolyte materials for inorganic all-solid-state batteries. Dopants and substituents like Al, Ta, Nb, Ga, and W were shown to have a high impact on the total ionic conductivity, increasing it from 10−6 S/cm up to 10−3 S/cm. However, natural zirconium sources always contain a small amount of hafnium which could also act as dopant, but the separation of these two elements is complicated and expensive. In this work, we investigate the influence of various Hf-impurity concentrations on the performance of tantalum-doped LLZO. We synthesised Li6.45Al0.05La3Zr1.6−xHfxTa0.4O12 (LLZHO with x = 0 – 1.6) via conventional solid-state synthesis and have demonstrated that up to x = 0.1, hafnium impurities do not have a significant impact on the performance of the material. Above this concentration, the Li-ion conductivity is steadily reduced to around 70% when zirconium is fully substituted by hafnium resulting in Li6.45Al0.05La3Hf1.6Ta0.4O12. As the purity of Zr precursors has a great impact on their price, these findings can help to reduce the price of LLZO in general, as lower grade zirconium can be used in industrial scale applications. [ABSTRACT FROM AUTHOR]

We have performed a detailed structural analysis of several crystals from the Sb2Te3−xSex solid solution (with x = 0–1.55) using a combination of single-crystal and powder X-ray diffraction and high-resolution scanning transmission electron microscope imaging combined with energy-dispersive X-ray spectroscopic mapping. The experimental study was supported by quantum-chemical calculations. All compounds crystallize in the rhombohedral tetradymite structure type in which the atoms occupy three symmetrically independent crystallographic sites; the two chalcogenide sites A1 and A2, and the antimony site Sb. They form quintuple A2–Sb–A1–Sb–A2 layers perpendicular to the [001] direction, held together via A2–A2 chalcogenide-chalcogenide interactions. The results of our experimental study show unambiguously, and in agreement with quantum-chemical calculations, a preferred incorporation of selenium into the A2 position inside the layers. An unexpected increase of the van-der-Waals inter-layer distances is observed for low Se contents (x < 1) and discussed with the help of DFT calculations. [ABSTRACT FROM AUTHOR]

We have performed a detailed structural analysis of several crystals from the Sb2Te3−xSex solid solution (with x = 0–1.55) using a combination of single-crystal and powder X-ray diffraction and high-resolution scanning transmission electron microscope imaging combined with energy-dispersive X-ray spectroscopic mapping. The experimental study was supported by quantum-chemical calculations. All compounds crystallize in the rhombohedral tetradymite structure type in which the atoms occupy three symmetrically independent crystallographic sites; the two chalcogenide sites A1 and A2, and the antimony site Sb. They form quintuple A2–Sb–A1–Sb–A2 layers perpendicular to the [001] direction, held together via A2–A2 chalcogenide-chalcogenide interactions. The results of our experimental study show unambiguously, and in agreement with quantum-chemical calculations, a preferred incorporation of selenium into the A2 position inside the layers. An unexpected increase of the van-der-Waals inter-layer distances is observed for low Se contents (x < 1) and discussed with the help of DFT calculations. [ABSTRACT FROM AUTHOR]

The high‐pressure and low‐temperature behaviour of the GeSexTe1−x system (x = 0, 0.2, 0.5, 0.75, 1) was studied using a combination of powder diffraction measurements and first‐principles calculations. Compounds in the stability field of the GeTe structure type (x = 0, 0.2, 0.5) follow the high‐pressure transition pathway: GeTe‐I (R3m) → GeTe‐II (f.c.c.) → GeTe‐III (Pnma). The newly determined GeTe‐III structure is isostructural to β‐GeSe, a high‐pressure and high‐temperature polymorph of GeSe. Pressure‐dependent formation enthalpies and stability regimes of the GeSexTe1−x polymorphs were studied by DFT calculations. Hexagonal Ge4Se3Te is stable up to at least 25 GPa. Significant differences in the high‐pressure and low‐temperature behaviour of the GeTe‐type structures and the hexagonal phase are highlighted. The role of Ge...Ge interactions is elucidated using the crystal orbital Hamilton population method. Finally, a sketch of the high‐pressure phase diagram of the system is provided. The high‐pressure and low‐temperature behaviour of the GeSexTe1−x system was studied using in situ diffraction and DFT calculations. The high‐pressure phase of GeTe‐III was determined. [ABSTRACT FROM AUTHOR]

Im ternären System Ge ‐ Se ‐ Te ist seit den 1960er Jahren eine hexagonale Phase mit der annähernden Zusammensetzung GeSe0.75Te0.25 bekannt, aber ihre Struktur blieb ungeklärt. Durch chemischen Transport gelang nun die Zucht von Einkristallen zur Bestimmung der Ge4Se3Te ‐ Struktur. Diese besteht aus Schichten, die – wie elektronenmikroskopische Analysen erhärten – über van ‐ der ‐ Waals ‐ artige schwache Chalkogen ‐ Chalkogen ‐ , aber auch über unerwartete Ge ‐ Ge ‐ Wechselwirkungen verbunden sind. Die Art der elektronischen Struktur von Ge4Se3Te wurde durch Analyse der chemischen Bindungen bestimmt, speziell mithilfe der neu eingeführten Energiedichte(DOE) ‐ Funktion. Die bindenden Ge ‐ Ge ‐ Wechselwirkungen dienen der Aufnahme von Elektronen, die ansonsten antibindende Ge ‐ Te ‐ Zustände einnähmen. Ge ‐ Ge ‐ Kontakte und die DOE: Ge4Se3Te, eine Schichtstruktur mit Van ‐ der ‐ Waals ‐ Wechselwirkungen und unerwarteten Ge ‐ Ge ‐ Kontakten, wurde kristallisiert, strukturell charakterisiert und auch elektronenmikroskopisch untersucht. Die Art der elektronischen Struktur wird durch Analyse der chemischen Bindungen und mithilfe der neu eingeführten Energiedichte(DOE) ‐ Funktion bestimmt. [ABSTRACT FROM AUTHOR]

A hexagonal phase in the ternary Ge-Se-Te system with an approximate composition of GeSe0.75Te0.25 has been known since the 1960s but its structure has remained unknown. We have succeeded in growing single crystals by chemical transport as a prerequisite to solve and refine the Ge4Se3Te structure. It consists of layers that are held together by van der Waals type weak chalcogenide-chalcogenide interactions but also display unexpected Ge-Ge contacts, as confirmed by electron microscopy analysis. The nature of the electronic structure of Ge4Se3Te was characterized by chemical bonding analysis, in particular by the newly introduced density of energy (DOE) function. The Ge-Ge bonding interactions serve to hold electrons that would otherwise go into antibonding Ge-Te contacts. [ABSTRACT FROM AUTHOR]

Transition metal-rich borides exhibit a diverse array of crystal structures and intriguing physical properties. Ti 2 FeOs 3 B 3 , an osmium-rich boride featuring B 4 zigzag fragments and iron dumbbell chains (Fe-ladder), was synthesized and investigated for its magnetic properties. Theoretical calculations reveal a strong competition between antiferromagnetic and ferromagnetic states with only around 8 meV per formula unit in favor of the former, thus predicting metamagnetic behavior. Magnetic measurements confirm an AFM transition (T N ≈ 25 K) at a low magnetic field of 0.01 T, but the ferromagnetic state prevails under the influence of stronger magnetic fields leading to a Curie temperature above room temperature (T C ≈ 650 K), suggesting that the weak AFM interchain Fe 2 –Fe 2 interactions at low fields have been completely flipped to FM interactions (θ ≈ 700 K) by the high magnetic field. This work highlights the complex interplay between composition, structure, and magnetic behavior in this compound and opens a new avenue for the discovery of magnetic materials based on the complex Ti 1+ x Rh 2- x + y Ir 3- y B 3 structure type. [Display omitted] • A new metamagnetic transition metal-rich boride Ti 2 FeOs 3 B 3 with Ti 1+ x Rh 2- x + y Ir 3- y B 3 structure type was discovered. • Crystal structure features B 4 zigzag fragments interacting with iron ladders. • DFT calculations reveal a strong competition between antiferromagnetic (AFM) and ferromagnetic (FM) states. • Shows AFM transition (T N ≈ 25 K) at a low magnetic field and FM state (T C ≈ 650 K) at high field. [ABSTRACT FROM AUTHOR]

The complex metal-rich boride Ti 5- x Fe 1- y Os 6+ x+y B 6 (0 < x , y < 1), crystallizing in a new structure type (space group Cmcm , no. 63), was prepared by arc-melting. The new structure contains both isolated boron atoms and zigzag boron chains (B-B distance of 1.74 Å), a rare combination among metal-rich borides. In addition, the structure also contains Fe-chains running parallel to the B-chains. Unlike in previously reported structures, these Fe-chains are offset from each other and arranged in a triangular manner with intrachain and interchain distances of 2.98 and 6.69 Å, respectively. Density functional theory (DFT) calculations predict preferred ferromagnetic interactions within each chain but only small energy differences for different magnetic interactions between them, suggesting a potentially weak long-range order. This new structure offers the opportunity to study new configurations and interactions of magnetic elements for the design of magnetic materials.

Solid electrolyte is the key component in all-solid-state batteries (ASBs). It is required in electrodes to enhance Li-conductivity and can be directly used as a separator. With its high Li-conductivity and chemical stability towards metallic lithium, lithium-stuffed garnet material Li 7 La 3 Zr 2 O 12 (LLZO) is considered one of the most promising solid electrolyte materials for high-energy ceramic ASBs. However, in order to obtain high conductivities, rare-earth elements such as tantalum or niobium are used to stabilize the highly conductive cubic phase. This stabilization can also be obtained via high levels of aluminum, reducing the cost of LLZO but also reducing processability and the Li-conductivity. To find the sweet spot for a potential market introduction of garnet-based solid-state batteries, scalable and industrially usable syntheses of LLZO with high processability and good conductivity are indispensable. In this study, four different synthesis methods (solid-state reaction (SSR), solution-assisted solid-state reaction (SASSR), co-precipitation (CP), and spray-drying (SD)) were used and compared for the synthesis of aluminum-substituted LLZO (Al:LLZO, Li 6.4 Al 0.2 La 3 Zr 2 O 12 ), focusing on electrochemical performance on the one hand and scalability and environmental footprint on the other hand. The synthesis was successful via all four methods, resulting in a Li-ion conductivity of 2.0-3.3 × 10 -4 S/cm. By using wet-chemical synthesis methods, the calcination time could be reduced from two calcination steps for 20 h at 850 °C and 1000 °C to only 1 h at 1000 °C for the spray-drying method. We were able to scale the synthesis up to a kg-scale and show the potential of the different synthesis methods for mass production.

A number of sesqui-chalcogenides show remarkable properties, which make them attractive for applications as thermoelectrics, topological insulators, and phase-change materials. To see if these properties can be related to a special bonding mechanism, seven sesqui-chalcogenides (Bi 2 Te 3 , Bi 2 Se 3 , Bi 2 S 3 , Sb 2 Te 3 , Sb 2 Se 3 , Sb 2 S 3 , and β-As 2 Te 3 ) and GaSe are investigated. Atom probe tomography studies reveal that four of the seven sesqui-chalcogenides (Bi 2 Te 3 , Bi 2 Se 3 , Sb 2 Te 3 , and β-As 2 Te 3 ) show an unconventional bond-breaking mechanism. The same four compounds evidence a remarkable property portfolio in density functional theory calculations including large Born effective charges, high optical dielectric constants, low Debye temperatures and an almost metal-like electrical conductivity. These results are indicative for unconventional bonding leading to physical properties distinctively different from those caused by covalent, metallic, or ionic bonding. The experiments reveal that this bonding mechanism prevails in four sesqui-chalcogenides, characterized by rather short interlayer distances at the van der Waals like gaps, suggestive of significant interlayer coupling. These conclusions are further supported by a subsequent quantum-chemistry-based bonding analysis employing charge partitioning, which reveals that the four sesqui-chalcogenides with unconventional properties are characterized by modest levels of charge transfer and sharing of about one electron between adjacent atoms. Finally, the 3D maps for different properties reveal discernible property trends and enable material design., (© 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The high-pressure and low-temperature behaviour of the GeSe x Te 1-x system (x = 0, 0.2, 0.5, 0.75, 1) was studied using a combination of powder diffraction measurements and first-principles calculations. Compounds in the stability field of the GeTe structure type (x = 0, 0.2, 0.5) follow the high-pressure transition pathway: GeTe-I (R3m) → GeTe-II (f.c.c.) → GeTe-III (Pnma). The newly determined GeTe-III structure is isostructural to β-GeSe, a high-pressure and high-temperature polymorph of GeSe. Pressure-dependent formation enthalpies and stability regimes of the GeSe x Te 1-x polymorphs were studied by DFT calculations. Hexagonal Ge 4 Se 3 Te is stable up to at least 25 GPa. Significant differences in the high-pressure and low-temperature behaviour of the GeTe-type structures and the hexagonal phase are highlighted. The role of Ge...Ge interactions is elucidated using the crystal orbital Hamilton population method. Finally, a sketch of the high-pressure phase diagram of the system is provided.

In 2 Se 3 has been known for over 100 years and recently attracted interest as a promising candidate for a variety of applications, such as solar cells, photodiodes, and phase-change memories. Despite the broad concern for possible uses, its polymorphism and structure are poorly characterized. By combining X-ray diffraction, transmission electron microscopy, and quantum-chemical calculations, we present here the crystal structures of two layered room-temperature polytypes: 3R and 2H In 2 Se 3 . Both polymorphs are stacking variants of the same Se-In-Se-In-Se layers comprising two coordination environments for the In atoms, one tetrahedral and one octahedral. By using chemical-bonding analysis, we look at the different In positions in α-In 2 Se 3 and compare them to those in the metastable β-phase.

A hexagonal phase in the ternary Ge-Se-Te system with an approximate composition of GeSe 0.75 Te 0.25 has been known since the 1960s but its structure has remained unknown. We have succeeded in growing single crystals by chemical transport as a prerequisite to solve and refine the Ge 4 Se 3 Te structure. It consists of layers that are held together by van der Waals type weak chalcogenide-chalcogenide interactions but also display unexpected Ge-Ge contacts, as confirmed by electron microscopy analysis. The nature of the electronic structure of Ge 4 Se 3 Te was characterized by chemical bonding analysis, in particular by the newly introduced density of energy (DOE) function. The Ge-Ge bonding interactions serve to hold electrons that would otherwise go into antibonding Ge-Te contacts., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)