High-entropy ceramics: Review of principles, production and applications

Akrami, Saeid; Edalati, Parisa; Fuji, Masayoshi; Edalati, Kaveh

doi:10.1016/j.mser.2021.100644

Cited by 365 publications

(211 citation statements)

References 735 publications

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“…High-entropy ceramics (HECs) [1][2][3], which can be generalized to a broader class of compositionally complex spinel [42] crystal structures, as well as more complex silicates [43], phosphates [44], aluminates [45,46], and molybates [47], have been studied. The vast majority of prior HEC studies focused on five-component equimolar compositions that produce ~1.61k B per cation ideal configurational entropy on at least one sublattice, where k B is the Boltzmann constant, but some studies also include four-component [20] and six-to ninecomponent [48] equimolar compositions [1][2][3]. Recent studies further investigated the high-entropy phase formation and transition in non-equimolar 10-and 11-component oxide systems, which can form either disordered (fluorite) or ordered (pyrochlore) phase (with either one or two cation sublattices) [31,49].…”

Section: Introduction mentioning

confidence: 99%

“…While the vast majority of prior studies investigated four- [20] to nine-component [48] (mostly equimolar) compositions [1][2][3], we propose to further explore (equimolar and non-equimolar) "many-component CCCs" (i.e., ≥ 10 components), which can offer even larger (and tailorable) compositional spaces and further (extreme) complexity (Fig. 1).…”

Section: Introduction mentioning

confidence: 99%

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21-Component compositionally complex ceramics: Discovery of ultrahigh-entropy weberite and fergusonite phases and a pyrochlore-weberite transition

et al. 2022

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Two new high-entropy ceramics (HECs) in the weberite and fergusonite structures, along with the unexpected formation of ordered pyrochlore phases with ultrahigh-entropy compositions and an abrupt pyrochlore-weberite transition, are discovered in a 21-component oxide system. While the Gibbs phase rule allows 21 equilibrium phases, 9 out of the 13 compositions examined possess single HEC phases (with ultrahigh ideal configurational entropies: ∼2.7kB per cation or higher on one sublattice in most cases). Notably, (15RE1/15)(Nb1/2Ta1/2)O4 possess a single monoclinic fergusonite (C2/c) phase, and (15RE1/15)3(Nb1/2Ta1/2)1O7 form a single orthorhombic (C2221) weberite phase, where 15RE1/15 represents Sc1/15Y1/15La1/15Pr1/15Nd1/15Sm1/15Eu1/15Gd1/15Tb1/15Dy1/15Ho1/15Er1/15Tm1/15 Yb1/15Lu1/15. Moreover, a series of eight (15RE1/15)2+x(Ti1/4Zr1/4Ce1/4H1/4)2−2x(Nb1/2Ta1/2)xO7 specimens all exhibit single phases, where a pyrochlore-weberite transition occurs within 0.75 < x < 0.8125. This cubic-to-orthorhombic transition does not change the temperature-dependent thermal conductivity appreciably, as the amorphous limit may have already been achieved in the ultrahigh-entropy 21-component oxides. These discoveries expand the diversity and complexity of HECs, towards many-component compositionally complex ceramics (CCCs) and ultrahigh-entropy ceramics.

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Section: Introduction mentioning

confidence: 99%

Section: Introduction mentioning

confidence: 99%

21-Component compositionally complex ceramics: Discovery of ultrahigh-entropy weberite and fergusonite phases and a pyrochlore-weberite transition

et al. 2022

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“…The HPT method is currently used as a severe plastic deformation technique 18 , 19 for controlling the crystal size 12 , 20 and phase transformation 21 , 22 in inorganic materials. The method is considered quite effective to connect atoms of various pure elements to generate larger molecules of metallic alloys 23 and multi-component ceramics 24 .…”

Section: Introductionmentioning

confidence: 99%

Glycine amino acid transformation under impacts by small solar system bodies, simulated via high-pressure torsion method

Edalati

Taniguchi

Floriano

et al. 2022

Sci Rep

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Impacts by small solar system bodies (meteoroids, asteroids, comets and transitional objects) are characterized by a combination of energy dynamics and chemical modification on both terrestrial and small solar system bodies. In this context, the discovery of glycine amino acid in meteorites and comets has led to a hypothesis that impacts by astronomical bodies could contribute to delivery and polymerization of amino acids in the early Earth to generate proteins as essential molecules for life. Besides the possibility of abiotic polymerization of glycine, its decomposition by impacts could generate reactive groups to form other essential organic biomolecules. In this study, the high-pressure torsion (HPT) method, as a new platform for simulation of impacts by small solar system bodies, was applied to glycine. In comparison with high-pressure shock experiments, the HPT method simultaneously introduces high pressure and deformation strain. It was found that glycine was not polymerized in the experimental condition assayed, but partially decomposed to ethanol under pressures of 1 and 6 GPa and shear strains of < 120 m/m. The detection of ethanol implies the inherent availability of remaining nitrogen-containing groups, which can incorporate to the formation of other organic molecules at the impact site. In addition, this finding highlights a possibility of the origin of ethanol previously detected in comets.

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“…For each specific temperature, the value of entropy is maximum for a solid solution with an equal concentration of mixing elements, when the number of such elements rises upward [ 18 ]. It is generally accepted from practice that solid solutions containing more than five elements of the same type with a concentration of 20% should be classified as high-entropy ones [ 19 ]. It follows from this that the condition for the existence of a high-entropy solid solution is that the entropy exceeds the value of 1.61 × R, where R is the universal gas constant [ 20 ].…”

Section: Introductionmentioning

confidence: 99%

A-Site Cation Size Effect on Structure and Magnetic Properties of Sm(Eu,Gd)Cr0.2Mn0.2Fe0.2Co0.2Ni0.2O3 High-Entropy Solid Solutions

et al. 2021

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Three high-entropy Sm(Eu,Gd)Cr0.2Mn0.2Fe0.2Co0.2Ni0.2O3 perovskite solid solutions were synthesized using the usual ceramic technology. The XRD investigation at room temperature established a single-phase perovskite product. The Rietveld refinement with the FullProf computer program in the frame of the orthorhombic Pnma (No 62) space group was realized. Along with a decrease in the V unit cell volume from ~224.33 Å3 for the Sm-based sample down to ~221.52 Å3 for the Gd-based sample, an opposite tendency was observed for the unit cell parameters as the ordinal number of the rare-earth cation increased. The average grain size was in the range of 5–8 μm. Field magnetization was measured up to 30 kOe at 50 K and 300 K. The law of approach to saturation was used to determine the Ms spontaneous magnetization that nonlinearly increased from ~1.89 emu/g (Sm) up to ~17.49 emu/g (Gd) and from ~0.59 emu/g (Sm) up to ~3.16 emu/g (Gd) at 50 K and 300 K, respectively. The Mr residual magnetization and Hc coercive force were also determined, while the SQR loop squareness, k magnetic crystallographic anisotropy coefficient, and Ha anisotropy field were calculated. Temperature magnetization was measured in a field of 30 kOe. ZFC and FC magnetization curves were fixed in a field of 100 Oe. It was discovered that the Tmo magnetic ordering temperature downward-curve decreased from ~137.98 K (Sm) down to ~133.99 K (Gd). The spin glass state with ferromagnetic nanoinclusions for all the samples was observed. The <D> average and Dmax maximum diameter of ferromagnetic nanoinclusions were calculated and they were in the range of 40–50 nm and 160–180 nm, respectively. The mechanism of magnetic state formation is discussed in terms of the effects of the A-site cation size and B-site poly-substitution on the indirect superexchange interactions.

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High-entropy ceramics: Review of principles, production and applications

Cited by 365 publications

References 735 publications

21-Component compositionally complex ceramics: Discovery of ultrahigh-entropy weberite and fergusonite phases and a pyrochlore-weberite transition

21-Component compositionally complex ceramics: Discovery of ultrahigh-entropy weberite and fergusonite phases and a pyrochlore-weberite transition

Glycine amino acid transformation under impacts by small solar system bodies, simulated via high-pressure torsion method

A-Site Cation Size Effect on Structure and Magnetic Properties of Sm(Eu,Gd)Cr0.2Mn0.2Fe0.2Co0.2Ni0.2O3 High-Entropy Solid Solutions

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