A new antimonide K8–x Zn18+3x Sb16 was synthesized using reactive potassium hydride KH as a precursor. Owing to intimate mixing of starting materials, the hydride route allows rapid phase “screening” of ternary systems and is particularly suitable for the search of new antimonides. The crystal structure of K8–x Zn18+3x Sb16 (x = 1.12(8); P42/nmc (no. 137), a = 12.3042(5) Å, c = 7.3031(3) Å, V = 1105.6(1) Å3, R 1 = 0.029) has a [Zn18Sb16] framework with large channels alternately filled by K cations and Zn3 triangular units. The Zn3 triangles break the channels into finite cages by forming covalent bonds to the framework, preventing K migration along the channel. This structural feature is responsible for its stability in air, uncommon for this class of compounds, as well as for its low thermal conductivity. Transport property measurement and computational analysis of the electronic structure indicate that the title compound is a semimetal with properties highly dependent on the precise composition, i.e., the K/Zn3 ratio in the channels. The hydride preparative route provides accurate control over the composition of the target phase, thereby facilitating transport properties tuning. This synthetic method will allow for the synthesis of novel alkali metal antimonides as well as for the development of functional materials via precise compositional control.

Ternary lithium nickel borides LiNi3B1.8 and Li2.8Ni16B8 have been synthesized by using reactive LiH as a precursor. This synthetic route allows better mixing of the precursor powders, thus facilitating rapid preparation of the alkali‐metal‐containing ternary borides. This method is suitable for “fast screening” of multicomponent systems comprised of elements with drastically different reactivities. The crystal structures of the compounds LiNi3B1.8 and Li2.8Ni16B8 have been re‐investigated by a combination of single‐crystal X‐ray/synchrotron powder diffraction, solid‐state 7Li and 11B NMR spectroscopies, and scanning transmission electron microscopy. This has allowed the determination of fine structural details, including the split position of Ni sites and the ordering of B vacancies. Field‐dependent and temperature‐dependent magnetization measurements are consistent with spin‐glass behavior for both samples.

Two new sodium zinc antimonides NaZn4Sb3 and HT-Na1-xZn4-ySb3 were synthesized by using reactive sodium hydride, NaH, as a precursor. The hydride route provides uniform mixing and comprehensive control over the composition, facilitating fast reactions and high-purity samples, whereas traditional synthesis using sodium metal results in inhomogeneous samples with a significant fraction of the more stable NaZnSb compound. NaZn4Sb3 crystalizes in the hexagonal P63/mmc space group (No. 194, Z = 2, a = 4.43579(4) Å, c = 23.41553(9) Å), and is stable upon heating in vacuum up to 736 K. The layered crystal structure of NaZn4Sb3 is related to the structure of the well-studied thermoelectric antimonides AeZn2Sb2 (Ae = Ca, Sr, Eu). Upon heating in vacuum NaZn4Sb3 transforms to HT-Na1-xZn4-ySb3 (x = 0.047(3), y = 0.135(1)) due to partial Na/Zn evaporation/elimination, as was determined from hightemperature in-situ synchrotron powder X-ray diffraction. HT-Na1-xZn4-ySb3 has a complex monoclinic structure with considerable degrees of structural disorder (P21/c (No. 14, Z = 32), a = 19.5366(7) Å, b = 14.7410(5) Å, c = 20.7808(7) Å, β = 90.317(2)°) and is stable exclusively in a narrow temperature range of 736 − 885 K. Further heating of HT-Na1-xZn4-ySb3 leads to a reversible transformation to NaZnSb above 883 K. Both compounds exhibit similarly low thermal conductivity at room temperature (0.9 W•m −1 K −1 ) and positive Seebeck coefficients (38-52 µV/K) indicative of holes as the main charge carriers. However, resistivities of the two phases differ by two orders of magnitude.Here, we have explored the ternary Na-Zn-Sb system and discovered two new compositionally similar, but structurally different ternary antimonides, both are featuring new structure types. Using the fast hydride route coupled with in-situ high-temperature powder X-ray diffraction experiments, compositional and temperature screening allowed for synthesis of two new ternary phases: NaZn4Sb3 phase and what at first appeared to be its polymorph, but in fact it is a different compound with slightly Na/Zn depleted composition HT-Na1-xZn4-ySb3, stable in narrow temperature range. The hydride route yields single phase samples of both antimonides, allowing for the experimental access to their transport properties. The crystal structures, synthesis, structural transformations, and transport properties of the NaZn4Sb3 and HT-Na1-xZn4-ySb3 are discussed herein.

Tw on ovel lithium nickel boride polymorphs,R T-LiNiB and HT-LiNiB,w ith layered crystal structures are reported. This family of compounds was theoretically predicted by using the adaptive genetic algorithm (AGA) and subsequently synthesized by ahydride route with LiH as the lithium source.U nique among the knownt ernary transition-metal borides,the LiNiB structures feature Li layers alternating with nearly planar [NiB] layers composed of Ni hexagonal rings with aB -B pair at the center.Acomprehensive study using ac ombination of single crystal/synchrotron powder X-ray diffraction, solid-state 7 Li and 11 BNMR spectroscopy, scanning transmission electron microscopy, quantum-chemical calculations,a nd magnetism has shed light on the intrinsic features of these polymorphic compounds.The unique layered structures of LiNiB compounds make them ultimate precursors for exfoliation studies,t hus paving aw ay toward twodimensional transition-metal borides,MBenes.

The pursuit of two-dimensional (2D) borides, MBenes, has proven to be challenging, not the least because of the lack of a suitable precursor prone to the deintercalation. Here, we studied room-temperature topochemical deintercalation of lithium from the layered polymorphs of the LiNiB compound with a considerable amount of Li stored in between [NiB] layers (33 at. % Li). Deintercalation of Li leads to novel metastable borides (Li∼0.5NiB) with unique crystal structures. Partial removal of Li is accomplished by exposing the parent phases to air, water, or dilute HCl under ambient conditions. Scanning transmission electron microscopy and solid-state 7Li and 11B NMR spectroscopy, combined with X-ray pair distribution function (PDF) analysis and DFT calculations, were utilized to elucidate the novel structures of Li∼0.5NiB and the mechanism of Li-deintercalation. We have shown that the deintercalation of Li proceeds via a “zip-lock” mechanism, leading to the condensation of single [NiB] layers into double or triple layers bound via covalent bonds, resulting in structural fragments with Li­[NiB]2 and Li­[NiB]3 compositions. The crystal structure of Li∼0.5NiB is best described as an intergrowth of the ordered single [NiB], double [NiB]2, or triple [NiB]3 layers alternating with single Li layers; this explains its structural complexity. The formation of double or triple [NiB] layers induces a change in the magnetic behavior from temperature-independent paramagnets in the parent LiNiB compounds to the spin-glassiness in the deintercalated Li∼0.5NiB counterparts. LiNiB compounds showcase the potential to access a plethora of unique materials, including 2D MBenes (NiB).