Design and synthesis of high-entropy pyrochlore ceramics based on valence combination

Jia, Huaiming; Li, Cuiwei; Chen, Guangjin; Li, Hao; Liu, Siyuan; An, Linan; Chen, Kepi

doi:10.1016/j.jeurceramsoc.2022.05.065

Cited by 16 publications

(5 citation statements)

References 28 publications

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“…extended the concept of high‐entropy from alloys to ceramics in 2015, then the study of high‐entropy ceramics grew in a blowout manner. The design of single‐phase high‐entropy ceramics could be guided by ionic radius, valence state, size disorder, and mass disorder, which was confirmed in high‐entropy pyrochlore oxides 17,18 . Moreover, severe lattice distortion caused by the multicomponent doping in high‐entropy ceramic has been considered an effective way to reduce the thermal conductivity 19–21 .…”

Section: Introductionmentioning

confidence: 98%

“…The design of single-phase high-entropy ceramics could be guided by ionic radius, valence state, size disorder, and mass disorder, which was confirmed in high-entropy pyrochlore oxides. 17,18 Moreover, severe lattice distortion caused by the multicomponent doping in high-entropy ceramic has been considered an effective way to reduce the thermal conductivity. [19][20][21] Especially, the size disorder and mass disorder are the important factors to evaluate the degree of lattice distortion.…”

Section: Introductionmentioning

confidence: 99%

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High‐entropy rare earth titanates with low thermal conductivity designed by lattice distortion

Zhu

et al. 2023

J Am Ceram Soc.

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High-entropy single-phase rare earth titanates (RE 0.2 Gd 0.2 Ho 0.2 Er 0.2 Yb 0.2 ) 2 Ti 2 O 7 (RE = Sm, Y, Lu) were designed and synthesized successfully, in which their lattice distortion was quantitatively described by mass disorder and size disorder. It is worth mentioning that (Y 0.2 Gd 0.2 Ho 0.2 Er 0.2 Yb 0.2 ) 2 Ti 2 O 7 could obtain the low thermal conductivity (1.51 W⋅m −1 ⋅K −1 , 1500 • C), high thermal expansion coefficient (average, 11.69×10 −6 K −1 , RT ∼1500 • C) and excellent high-temperature stability. In addition, the relationship between the microstructure and thermal transport behaviors has been studied at the atomic scale. Due to the disorder of A-site ions, severe lattice distortion occurred in specific crystal planes, and the large mass difference between Y 3+ and other RE 3+ further causes mass fluctuation and results in lower thermal conductivity. Compared with YSZ, the high-entropy rare earth titanate (Y 0.2 Gd 0.2 Ho 0.2 Er 0.2 Yb 0.2 ) 2 Ti 2 O 7 has lower thermal conductivity, higher thermal expansion coefficient, and excellent high-temperature stability, which has great potential for application in the thermal protection field.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

High‐entropy rare earth titanates with low thermal conductivity designed by lattice distortion

Zhu

et al. 2023

J Am Ceram Soc.

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“…In 2015, Rost et al were the first to synthesize entropy-stabilized oxides (MgCoNiCuZn)O with a rock salt structure, extending high-entropy materials from alloys to oxides [ 4 ]. At present, a large number of high-entropy oxides (HEOs) with different structures were synthesized, including a fluorite [ 5 , 6 , 7 , 8 ], pyrochlore [ 9 , 10 , 11 , 12 ], spinel [ 13 , 14 , 15 , 16 ], and perovskite structure [ 17 , 18 , 19 , 20 , 21 ], and so on [ 22 , 23 ]. Nevertheless, many researchers have committed to exploring new possibilities of entropy-stabilized HEO systems.…”

Section: Introductionmentioning

confidence: 99%

The Formation and Phase Stability of A-Site High-Entropy Perovskite Oxides

et al. 2023

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High entropy perovskite oxides (HEPOs) were a class of advanced ceramic materials, which had attracted much scientific attention in recent years. However, the effect of factors affecting the phase stability of high entropy perovskite oxides was still controversial. Herein, 17 kinds of A-site HEPOs were synthesized by solid-state methods, and several criteria for the formation of HEPOs and phase stability were investigated. Single-phase solid solutions were synthesized in 12 kinds of subsystems. The results show that the phase stability of a single-phase solid solution was affected by the size disorder and configurational entropy. The electronegativity difference was the key parameter to predict the evolution of the cubic/tetragonal phase, rather than the tolerance factor. Cubic HEPOs were easily formed when the electronegativity difference was <0.4, while the tetragonal HEPOs were easily formed when the electronegativity difference was ≥0.4. This study can further broaden the family of HEPOs and is expected to design the phase stability of HEPOs through electronegativity difference.

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“…Very recently, Jia et al. reported on the possibility to design new high‐entropy pyrochlores, 20 using the “valence combination” method. Thus, five new compounds (with the disorder introduced on the B site) were synthesized, namely, La 2 (ZrYYbNbTa) 2 O 7 , La 2 (ZrHfSnYbNb) 2 O 7 , Y 2 (TiZrHfGeSn) 2 O 7 , La 2 (Ti 0.1 Zr 0.3 Sn 0.3 Yb 0.15 Nb 0.15 ) 2 O 7 , and La 2 (Ti 0.1 Zr 0.3 Hf 0.2 Ce 0.1 Sn 0.3 ) 2 O 7 .…”

Section: Introductionmentioning

confidence: 99%

“…8 To the best of our knowledge, since then the reported high-entropy pyrochlores with chemical disorder introduced on the B site are RE 2 (TiZrHfSn) 2 O 7 (RE = Sm or Gd) 15,16 ; Y 2 (TiZrHfMoV) 2 O 7 , Y 2 (TiZrHfV) 2 O 7 , and Y 2 (TiZrHfMo) 2 O 7 17 ; RE 2 (ZrHfSnScNb) 2 O 7 and RE 2 (ZrHfSnScTa) 2 O 7 (RE = La or Nd) 18 ; and the two distorted pyrochlores Nd 2 (ZrHfSnScTa) 2 O 7 and Nd 2 (ZrHfSnTiNb) 2 O 7 . 19 Very recently, Jia et al reported on the possibility to design new highentropy pyrochlores, 20 using the "valence combination" method. Thus, five new compounds (with the disorder introduced on the B site) were synthesized, namely, La 2 (ZrYYbNbTa) 2 O 7 , La 2 (ZrHfSnYbNb) 2 O 7 , Y 2 (TiZrHfGeSn) 2 O 7 , La 2 (Ti 0.1 Zr 0.3 Sn 0.3 Yb 0.15 Nb 0.15 ) 2 O 7 , and La 2 (Ti 0.1 Zr 0.3 Hf 0.2 Ce 0.1 Sn 0.3 ) 2 O 7 .…”

Section: Introductionmentioning

confidence: 99%

Investigation of the chemical versatility in high‐entropy pyrochlores

et al. 2022

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This article reports on the exploration of the chemical versatility of entropy‐stabilized pyrochlores (A2B2O7) with large chemical disorder introduced on the B site, as well as the study of isovalent and aliovalent substitution on the B site and of Ca2+‐doping on the A site. Among all the 20 new compounds obtained in this study, 8 are entropy‐stabilized: RE2(TiZrHfGeSn)2 (with RE = Gd–Ho and Y), Pr2(TiZrHfScNb)2O7, and RE2(TiGeSnAlNb)2O7 (with RE = Er and Y). Moreover, some physical properties (magnetic, electrical, thermal, and optical properties) of these high‐entropy pyrochlores have been screened, and some of them could be potentially interesting for applications. For example, we observed low thermal diffusivity values (between 0.4 and 0.7 m2 s−1) making them interesting for thermal barrier coating or tunable optical bandgaps in the visible region that could make them appealing as photocatalysts or in optical applications. Furthermore, single‐phased compounds were obtained for almost all the rare earths (REs) on the A site. Therefore, when five nonmagnetic cations are used for the B site, it enables to study the magnetic properties and, more specifically, the influence of the local chemical and structural disorder on the exotic ground states observed in monocationic RE pyrochlores.

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Design and synthesis of high-entropy pyrochlore ceramics based on valence combination

Cited by 16 publications

References 28 publications

High‐entropy rare earth titanates with low thermal conductivity designed by lattice distortion

High‐entropy rare earth titanates with low thermal conductivity designed by lattice distortion

The Formation and Phase Stability of A-Site High-Entropy Perovskite Oxides

Investigation of the chemical versatility in high‐entropy pyrochlores

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