This viewpoint article focuses on some of the important issues related to the emerging field of high entropy oxides (HEOs). Open queries regarding the role of entropy, enthalpy, individual elements ...and synergy arising from the presence of multiple elements in HEOs are discussed. In addition, a brief overview of the current state of research on HEOs is provided. Finally, we share our views on the uniqueness of HEOs by describing some features, which distinguish them from the conventional oxides.
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Magnetic properties of high entropy oxides Sarkar, Abhishek; Kruk, Robert; Hahn, Horst
Dalton transactions : an international journal of inorganic chemistry,
02/2021, Letnik:
5, Številka:
6
Journal Article
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Odprti dostop
High entropy oxides (HEOs) are single phase solid solutions consisting of five or more elements in equiatomic or near-equiatomic proportions incorporated into the cationic sub-lattice(s). The ...uniqueness of the HEOs lies in their extreme chemical complexity enveloped in a single crystallographic structure, which in many cases results in novel functionalities. From the local structure perspective, HEOs consist of an unusually large number of different metal-oxygen-metal couples. Consequently, magnetic correlations in HEOs that inherently depend on the coordination geometry, valence, spin state and type of the metal cations that are hybridized with the bridging oxygen, are naturally affected by an extreme diversity of neighboring ionic configurations. In these conditions, a complex magneto-electronic free-energy landscape in HEOs can be expected, potentially leading to stabilization of unconventional spin-electronic states. This Frontier article provides an overview of the unique magnetic features stemming from the extreme chemical disorder in HEOs along with the possible opportunities for further research and exploration of potential functionalities.
This Frontier article highlights the distinctive magnetic properties of high entropy oxides and the possible research directions for future explorations.
Quantification of gene expression levels at the single cell level has revealed that gene expression can vary substantially even across a population of homogeneous cells. However, it is currently ...unclear what genomic features control variation in gene expression levels, and whether common genetic variants may impact gene expression variation. Here, we take a genome-wide approach to identify expression variance quantitative trait loci (vQTLs). To this end, we generated single cell RNA-seq (scRNA-seq) data from induced pluripotent stem cells (iPSCs) derived from 53 Yoruba individuals. We collected data for a median of 95 cells per individual and a total of 5,447 single cells, and identified 235 mean expression QTLs (eQTLs) at 10% FDR, of which 79% replicate in bulk RNA-seq data from the same individuals. We further identified 5 vQTLs at 10% FDR, but demonstrate that these can also be explained as effects on mean expression. Our study suggests that dispersion QTLs (dQTLs) which could alter the variance of expression independently of the mean can have larger fold changes, but explain less phenotypic variance than eQTLs. We estimate 4,015 individuals as a lower bound to achieve 80% power to detect the strongest dQTLs in iPSCs. These results will guide the design of future studies on understanding the genetic control of gene expression variance.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The enhanced compositional flexibility to incorporate multiple-principal cations in high entropy oxides (HEOs) offers the opportunity to expand boundaries for accessible compositions and ...unconventional properties in oxides. Attractive functionalities have been reported in some bulk HEOs, which are attributed to the long-range compositional homogeneity, lattice distortion, and local chemical bonding characteristics in materials. However, the intricate details of local composition fluctuation, metal-oxygen bond distortion and covalency are difficult to visualize experimentally, especially on the atomic scale. Here, we study the atomic structure-chemical bonding-property correlations in a series of perovskite-HEOs utilizing the recently developed four-dimensional scanning transmission electron microscopy techniques which enables to determine the structure, chemical bonding, electric field, and charge density on the atomic scale. The existence of compositional fluctuations along with significant composition-dependent distortion of metal-oxygen bonds is observed. Consequently, distinct variations of metal-oxygen bonding covalency are shown by the real-space charge-density distribution maps with sub-ångström resolution. The observed atomic features not only provide a realistic picture of the local physico-chemistry of chemically complex HEOs but can also be directly correlated to their distinctive magneto-electronic properties.
High‐entropy materials, especially high‐entropy alloys and oxides, have gained significant interest over the years due to their unique structural characteristics and correlated possibilities for ...tailoring of functional properties. The developments in the area of high‐entropy oxides are highlighted here, with emphasis placed on their fundamental understanding, including entropy‐dominated phase‐stabilization effects and prospective applications, e.g., in the field of electrochemical energy storage. Critical comments on the different classes of high‐entropy oxides are made and the underlying principles for the observed properties are summarized. The diversity of materials design, provided by the entropy‐mediated phase‐stabilization concept, allows engineering of new oxide candidates for practical applications, warranting further studies in this emerging field of materials science.
High‐entropy oxides have gained significant interest over the years due to their chemical complexity, and they provide a novel strategy for materials design to tailor properties for targeted applications. The entropy‐based stabilization concept not only renders the possibility of influencing the phase stability of a multicationic system, but also affects their functional properties.
In recent years, the concept of entropy stabilization of crystal structures in oxide systems has led to an increased research activity in the field of "high entropy oxides". These compounds comprise ...the incorporation of multiple metal cations into single-phase crystal structures and interactions among the various metal cations leading to interesting novel and unexpected properties. Here, we report on the reversible lithium storage properties of the high entropy oxides, the underlying mechanisms governing these properties, and the influence of entropy stabilization on the electrochemical behavior. It is found that the stabilization effect of entropy brings significant benefits for the storage capacity retention of high entropy oxides and greatly improves the cycling stability. Additionally, it is observed that the electrochemical behavior of the high entropy oxides depends on each of the metal cations present, thus providing the opportunity to tailor the electrochemical properties by simply changing the elemental composition.
In the present work, a new class of high entropy materials for energy storage applications is introduced. Multi-anionic and -cationic compounds are prepared by facile mechanochemistry using a ...recently designed multi-cationic transition-metal-based high entropy oxide as the precursor and LiF or NaCl as the reactant, leading to formation of lithiated or sodiated materials. Notably, the Li-containing entropy-stabilized oxyfluoride described herein (Li
x
(Co
0.2
Cu
0.2
Mg
0.2
Ni
0.2
Zn
0.2
)OF
x
) exhibits a working potential of 3.4 V
vs.
Li
+
/Li, enabling its use as a cathode active material. Unlike conventional (non-entropy-stabilized) oxyfluorides, this new material shows enhanced Li storage properties due to entropy stabilization, which, in general, facilitates tailoring the cycling performance by varying the constituent elements in yet unprecedented ways. In addition, we demonstrate that the concept of entropy stabilization is also applicable to Na-containing oxychlorides with a rock-salt structure, thus paving the way toward development of (next-generation) post-Li battery technologies.
For the first time, a multi-anionic and multi-cationic high entropy oxyhalide is presented as high capacity cathode for Li-ion batteries.
Owing to their robust Li-ion storage properties induced by the entropy stabilization effect, transition-metal-based high entropy oxides are considered promising electrode materials for use in Li-ion ...batteries. In this work, full-cells comprising (Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)O anode and LiNi1/3Co1/3Mn1/3O2 cathode were assembled to explore their potential for practical applications. The cycling performance was studied by different electrochemical experiments. The cells were found to deliver an initial specific discharge capacity of 446 mAh g−1, which was maintained at 300 and 256 mAh g−1 after 50 and 100 cycles, respectively, and they showed stable cyclability even at specific currents of 1.6 A g−1. More importantly, high specific energy and power densities of about 240 Wh kg−1 and 320 W kg−1 were achieved. Additionally, pouch cells of total capacity 2.5 mAh were built and successfully employed as a power source.
•First application of high entropy oxides as a viable anode active material for Li-ion full-cells•Even non-optimized NCM111//TM-HEO pouch and coin-cells exhibit promising cycling performance at various current loads.•Specific energy densities as high as 240 Wh kg−1 can be achieved readily.
Layered Delafossite-type Li
(M
M
M
M
M
…M
)O
materials, a new class of high-entropy oxides, were synthesized by nebulized spray pyrolysis and subsequent high-temperature annealing. Various metal ...species (M = Ni, Co, Mn, Al, Fe, Zn, Cr, Ti, Zr, Cu) could be incorporated into this structure type, and in most cases, single-phase oxides were obtained. Delafossite structures are well known and the related materials are used in different fields of application, especially in electrochemical energy storage (e.g., LiNi
Co
Mn
O
NCM). The transfer of the high-entropy concept to this type of materials and the successful structural replication enabled the preparation of novel compounds with unprecedented properties. Here, we report on the characterization of a series of Delafossite-type high-entropy oxides by means of TEM, SEM, XPS, ICP-OES, Mössbauer spectroscopy, XRD including Rietveld refinement analysis, SAED and STEM mapping and discuss about the role of entropy stabilization. Our experimental data indicate the formation of uniform solid-solution structures with some Li/M mixing.
Homogeneous distribution of the constituent elements at the atomic scale in high entropy oxides (HEOs) was demonstrated for the first time by atom probe tomography (APT). Three different single-phase ...HEOs having rocksalt, fluorite, and perovskite type crystal structures were synthesized using nebulized spray pyrolysis process. The as-synthesized powders were compacted into pellets under high pressure of 6 GPa. Both as-synthesized and compacted powders were investigated by X-ray diffraction and transmission electron microscopy. APT results showed that the constituent cations in all three HEO systems were homogenously distributed with no significant segregation or concentration fluctuation even at the atomic scale.
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