A five-component entropy-stabilized fluorite oxide

Chen, Kepi; Pei, Xintong; Tang, Lei; Cheng, Huhu; Li, Zemin; Li, Cuiwei; Zhang, Xiaowen; An, Linan

doi:10.1016/j.jeurceramsoc.2018.04.063

Cited by 280 publications

(138 citation statements)

References 15 publications

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“…Typically in the case of (MgCoNiCuZn)O, the first canonical composition reported in 2015 by Rost et al, a simple rock salt structure where the cations are distributed randomly on the cationic sublattice is formed when a mixture of the binary constituents is heated above 875°C, and the resulting entropy‐stabilized structure decomposes if further annealed below 875°C . Other structures have been observed since 2015 with other compositions, including perovskite or fluorite structures . We have shown previously that the rock salt phase obtained in the case of (MgCoNiCuZn)O is very robust against substitutions, due to charge compensation mechanism(s) that keep the charge balance between the cationic and anionic sublattices .…”

Section: Introductionmentioning

confidence: 71%

“…4 Other structures have been observed since 2015 with other compositions, including perovskite 5,6 or fluorite structures. 7 We have shown previously that the rock salt phase obtained in the case of (MgCoNiCuZn)O is very robust against substitutions, due to charge compensation mechanism(s) that keep the charge balance between the cationic and anionic sublattices. 8 rock salt structure is maintained up to at least x = 0.3 and the materials remain electrically insulating.…”

Section: Introductionmentioning

confidence: 97%

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Charge compensation mechanisms in Li‐substituted high‐entropy oxides and influence on Li superionic conductivity

et al. 2019

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The charge compensation mechanisms that occur when Li+ substitutes a 2+ element in superionic conductor (MgCoNiCuZn)O high‐entropy oxide have been studied using a combination of thermogravimetric analysis and X‐ray photoemission spectroscopy. Depending on the concentration of Li+ in the compound, the charge compensation involves first partial oxidation of Co2+ into Co3+ for low fraction of Li+, and then a combination of both the oxidation of cobalt and the formation of oxygen vacancies for large fraction of Li+.

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Section: Introductionmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 97%

Charge compensation mechanisms in Li‐substituted high‐entropy oxides and influence on Li superionic conductivity

et al. 2019

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“…To the best of our knowledge, all of the previously reported single‐phase high‐entropy oxide ceramics synthesized using conventional solid‐state reaction were subjected to fast cooling, such as air quenching or rapid cooling by turning off the furnace, which is common for high‐entropy materials in order to preserve the entropy‐stabilized phases that are favorably formed at high temperatures …”

Section: Introductionmentioning

confidence: 99%

Solid‐state synthesis of multicomponent equiatomic rare‐earth oxides

et al. 2020

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Phase formation in multicomponent rare-earth oxides is determined by a combination of composition, sintering atmosphere, and cooling rate. Polycrystalline ceramics comprising various combinations of Ce, Gd, La, Nd, Pr, Sm, and Y oxides in equiatomic proportions were synthesized using solid-state sintering. The effects of composition, sintering atmosphere, and cooling rate on phase formation were investigated. Single cubic or monoclinic structures were obtained with a slow cooling of 3.3°C/min, confirming that rare-earth oxides follow a different structure stabilization process than transition metal high-entropy oxides. In an oxidizing atmosphere, both Ce and Pr induce a cubic structure, while only Ce plays that role in an inert or reducing atmosphere. Samples without Ce or Pr develop a single monoclinic structure. The structures formed at initial synthesis may be converted to a different one, when the ceramics are annealed in an additional atmosphere. Phase evolution of a five-cation composition was also studied as a function of sintering temperature. The binary oxides used as raw materials completely dissolve into a single cubic structure at 1450°C in air. K E Y W O R D S phase transformations, rare earths, reaction sintering How to cite this article: Pianassola M, Loveday M, McMurray JW, Koschan M, Melcher CL, Zhuravleva M. Solid-state synthesis of multicomponent equiatomic rare-earth oxides. J Am Ceram Soc.

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“…For instance, several single‐phase multicomponent metal diborides and metal carbide systems were synthesized, the synthesized ceramic structures had ultra‐high temperature properties coupled with low values of thermal conductivity . The concept of entropy stabilization was further used to synthesize more complex spinel, perovskite and fluorite crystal structures . The transition metal ion stabilized rock salt structure ([MgNiCoCuZn]O) is of particular interest because of the high potential exhibited by this material system for various properties …”

Section: Introductionmentioning

confidence: 99%

Critical role of cationic local stresses on the stabilization of entropy‐stabilized transition metal oxides

2020

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Entropy‐stabilized transition metal oxides ([MgNiCoCuZn]O) (ESO) in recent years have received considerable attention owing to their unique functional properties. Solution combustion and solid state syntheses resulted in crystallites varying from 5‐15 nm to 3‐5 μm respectively. Phase stability studies showed that all the systems containing Cu2+ ions in the ESO lattice segregated upon slow cooling in the furnace. It was only when ESO was quenched in air from 1000°C the lattice stabilized to a single phase. Experiments concomitant with molecular dynamics (MD) simulations demonstrated that the local stress fields around the cations played a critical role in stabilizing the single phase. The local stress fields are a result of Jahn‐Teller distortion induced by the Cu2+ ions in the lattice. It is clearly established that in the absence of the minimization of the local stress fields around the Cu2+ ions, segregation leading to the formation of a multi‐phase material is imminent for this particular composition.

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A five-component entropy-stabilized fluorite oxide

Cited by 280 publications

References 15 publications

Charge compensation mechanisms in Li‐substituted high‐entropy oxides and influence on Li superionic conductivity

Charge compensation mechanisms in Li‐substituted high‐entropy oxides and influence on Li superionic conductivity

Solid‐state synthesis of multicomponent equiatomic rare‐earth oxides

Critical role of cationic local stresses on the stabilization of entropy‐stabilized transition metal oxides

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