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Diffusion-enhanced hydride synthesis enables the modern solidstate chemist to achieve their Hephaestian aspirations through design of experiments methods and the mechanistic knowledge gleaned fromin situpowder X-ray diffraction data. 

Non-oxidized SiNSs are effectively non-emissive (Φ_PL< 0.6%) while previously reported photoluminescent properties (Φ_PL> 8%) originate from oxidation of the silicon backbone. 

Kagome compounds have garnered attention in the past few years for their intriguing magnetic properties arising from spin frustration dictated by the geometry of the Kagome sublattice. In this paper, we highlight the success of the unconventional hydride route for the fast and easy synthesis of the Kagome compound KV6Sb6. High-temperature in situ powder x-ray diffraction (PXRD) studies proved to be useful in hinting at the existence of KV6Sb6, identifying its synthesis conditions, and understanding the reaction mechanism. The crystal structure for KV6Sb6 was determined from high-resolution PXRD data. The compound has a layered structure [R¯3m,a=5.5318(9)Å, c=34.23(3)Å, V=907.0(8)Å3, Z=3 at room temperature] and features a Kagome bilayer of V atoms. KV6Sb6 is isostructural to the previously reported RbV6Sb6 and CsV6Sb6 compounds. KV6Sb6 is thermally stable in vacuum up to 1173 K, as evident from the high-temperature in situ PXRD and differential scanning calorimetric analysis. Investigation of magnetic properties for KV6Sb6 between 2 and 300 K reveals temperature-independent paramagnetism and an absence of superconductivity, like the Rb and Cs analogs. Furthermore, we compare the magnetic properties of KV3Sb5, another ternary Kagome compound, synthesized via two different methods: the hydride route and the traditional route from elements. Low-temperature transport property measurements of KV6Sb6 indicate metallic behavior and an intrinsically low thermal conductivity of 1.0WK−1m−1 at 300 K. The layered structure of KV6Sb6 makes it an attractive candidate for deintercalation and doping studies to tune both magnetic and transport properties, laying a foundation for further studies. 

Combined experimental and density functional theory (DFT) study of Pr0.75Gd0.25ScGe and its hydride (Pr0.75Gd0.25ScGeH) reveals intricacies of composition-structure-property relationships in those distinctly layered compounds. Hydrogenation of the intermetallic parent, crystalizing in a tetragonal CeScSi-type structure, leads to an anisotropic volume expansion, that is, a(=b) lattice parameter decreases while the lattice expands along the c direction, yielding a net increase of cell volume. DFT calculations predict an antiparallel coupling of localized Gd and Pr magnetic moments in both materials at the ground state. While experiments corroborate this for the parent compound, there is no conclusive experimental proof for the hydride, where Pr moments do not order down to 3 K. DFT results also reveal that rare-earth – hydrogen interactions reduce spin-polarization of the Pr and Gd 5d and Sc 3d states at the Fermi energy, disrupt indirect exchange interactions mediated by conduction electrons, dramatically reduce the magnetic ordering temperature, and open a pseudo-gap in the majority-spin channel. Both experiments and theory show evidence of Kondo-like behavior in the hydride in the absence of an applied magnetic field, whereas increasing the field promotes magnetic ordering and suppresses Kondo-like behavior. 

Doping, or incremental substitution of one element for another, is an effective way to tailor a compound’s structure as well as its physical and chemical properties. Herein, we replaced up to 30% of Ni with Co in members of the family of layered LiNiB compounds, stabilizing the high-temperature polymorph of LiNiB while the room-temperature polymorph does not form. By studying this layered boride with in situ high-temperature powder diffraction, we obtained a distorted variant of LiNi0.7Co0.3B featuring a perfect interlayer placement of [Ni0.7Co0.3B] layers on top of each other─a structural motif not seen before in other borides. Because of the Co doping, LiNi0.7Co0.3B can undergo a nearly complete topochemical Li deintercalation under ambient conditions, resulting in a metastable boride with the formula Li0.04Ni0.7Co0.3B. Heating of Li0.04Ni0.7Co0.3B in anaerobic conditions led to yet another metastable boride, Li0.01Ni0.7Co0.3B, with a CoB-type crystal structure that cannot be obtained by simple annealing of Ni, Co, and B. No significant alterations of magnetic properties were detected upon Co-doping in the temperature-independent paramagnet LiNi0.7Co0.3B or its Li-deintercalated counterparts. Finally, Li0.01Ni0.7Co0.3B stands out as an exceptional catalyst for the selective hydrogenation of the vinyl C═C bond in 3-nitrostyrene, even in the presence of other competing functional groups. This research showcases an innovative approach to heterogeneous catalyst design by meticulously synthesizing metastable compounds.