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High-entropy materials, with complex compositions and unique cocktail characteristics, have recently drawn significant attention. Additionally, a family of sodium super ion conductors (NASICONs)-structured phosphates in energy storage areas shows a comprehensive application for traditional alkaline ion batteries and, in particular, solid-state electrolytes. However, there is no precedent in fabricating this kind of NASICON-type high-entropy phase. Here, we report the successful fabrication of two well-crystallized high-entropy phosphates, namely, Na3(Ti0.2V0.2Mn0.2Cr0.2Zr0.2)2(PO4)3(HE-N3M2P3) and Na(Ti0.2V0.2Mn0.2Cr0.2Zr0.2)2PO4Ox(HE-NMP). The prepared materials in which the transition metals (TMs) of Ti, V, Mn, Cr, and Zr occupy the same 12c Wykoff position can form a structure analogous to R3̅cNa3V2(PO4)3that is carefully determined by X-ray diffraction, neutron diffraction, and transmission electron microscopy. Further, their performance for sodium ion batteries and sodium-based solid-state electrolytes was evaluated. The HE-N3M2P3might exhibit a promising electrochemical performance for sodium storage in terms of its structure resembling that of Na3V2(PO4)3. Meanwhile, the HE-NMP shows considerable electrochemical activity with numerous broad redox ranges during extraction and insertion of Na+, related to the coexistence of several TM elements. The evaluated temperature-dependent ionic conductivity for HE-NMP solid electrolyte varies from 10–6to 10–5S cm–1from room temperature to 398.15 K, offering high potential for energy storage applications as a new high-entropy system.

For the first time, we report on the structural and magnetic properties of a polycrystalline sample of Ni4Nb2O9from I-type (Fdd2), obtained by the partial cosubstitution of Nb5+by Ti4+and W6+. The crystal structure is investigated by combining synchrotron X-ray, neutron, and electron diffraction at room temperature. This I-type structure is derived from the corundum-like Ni4Nb2O9II-type (Pbcn) and is noncentrosymmetric and polar. The Ni-lattice is composed of the stacking of distorted honeycomb layers with double zigzag ribbons 60° disoriented from each other in two successive double layers. The connection between layers is ensured by the sharing of octahedra faces building (Nb,W,Ti)2O9, Ni2O9, and Ni3O12units. This study shows how the disruption of the Nb2O6units by smaller d0cations impacts the structure, significantly modifying the Ni network and, thus, the magnetic properties. The latter were studied by dc- and ac-magnetic susceptibility, and the magnetic structure was solved by neutron powder diffraction. A ferrimagnetic behavior occurs below 68 K, followed by a re-entrant spin-glass-like behavior below ≈50 K.

Al4SiC4is a ternary wide-band-gap semiconductor with a high strength-to-weight ratio and excellent oxidation resistance. It consists of slabs of Al4C3separated by SiC layers with the space group of P63mc. The space group allows Si to occupy two different 2aWykoff sites, with previous studies reporting that Si occupies only one of the two sites, giving it an ordered structure. Another hitherto unexplored possibility is that Si can be randomly distributed on both 2asites. In this work, we revisit the published ordered crystal structure using experimental methods and density functional theory (DFT). Al4SiC4was synthesized by high-temperature sintering at 1800 °C from a powder mixture of Al4C3and SiC. Neutron diffraction confirmed that Al4SiC4crystallized with the space group of P63mc, with diffraction patterns that could be fitted to both the ordered and the disordered structures. Scanning transmission electron microscopy, however, provided clear evidence supporting the latter, with DFT calculations further confirming that it is 0.16 eV lower in energy per Al4SiC4formula unit than the former. TEM analysis revealed Al vacancies in some of the atomic layers that can introduce p-type doping and direct band gaps of 0.7 and 1.2 eV, agreeing with our optical measurements. Finally, we propose that although the calculated formation energy of the Al vacancies is high, the vacancies are stabilized by entropy effects at the high synthesis temperature. This indicates that the cooling procedure after high-temperature synthesis can be important in determining the vacancy content and the electronic properties of Al4SiC4.

Polycrystalline Nd1−xSrxFeO3−δ(0.1 ≤ x≤ 0.9) samples exhibit a single-phase perovskite-type crystal structure and G-type antiferromagnetism with small ferromagnetic order. Assuming that the Fe site is in the mixed-valence state, the spin state of Fe changes from a low-spin (LS) or intermediate spin Fe3+-dominant state at x≤ 0.5 to a LS Fe4+dominant state at x≥ 0.6. This strongly suggests that the charge carriers change from holes to electrons. In fact, at temperatures less than 500 K, these samples show a p-type Seebeck coefficient for 0.1 ≤ x≤ 0.5 and an n-type Seebeck coefficient for 0.6 ≤ x≤ 0.9. However, for 0.6 ≤ x≤ 0.9, Fe4+is reduced to Fe3+because of an oxygen deficiency in the 500–600 K temperature range. In particular, Nd0.7Sr0.3FeO2.99(1)shows the largest p-type ZT= 0.025 at 765 K, whereas compositions with high n-type ZTcould not be identified.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.