High entropy defective fluorite structured rare-earth niobates and tantalates for thermal barrier applications

Zhao, Zifan; Chen, Heng; Xiang, Huimin; Dai, Fu‐Zhi; Wang, Xiaohui; Xu, Wei; Sun, Kuang; Peng, Zhijian; Zhou, Yanchun

doi:10.1007/s40145-020-0368-7

Cited by 143 publications

(72 citation statements)

References 38 publications

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“…Inspired by the pioneering work of Rost et al [29], most of the researches focus on the synthesis and property exploring of entropy stabilized oxides. Shortly, oxides with rock salt [21,29,[63][64][65][66][67], fluorite [38,60,[68][69][70][71], pyrochlore [36,37,[72][73][74][75], and spinel [80][81][82][83] structures were explored and fascinating properties brought by high-entropy effects have been reported. Gild et al [34] extended the material systems to ultrahigh temperature ceramics (UHTCs) by fabricating high-entropy borides with AlB 2 structure.…”

Section: Electronic Structure and Band Gap Engineeringmentioning

confidence: 99%

“…Taking the advantages of tunable thermal expansion coefficient, high hardness, slow grain growth rate, and better stability, HEC thin films and coatings show great potential in the field of thermal/environmental barrier coatings (TBC/EBCs) [23,37,71,85,[87][88][89][90]93,149], hard coatings, oxidation and corrosion resistant coatings [150][151][152][153][154][155][156][157]. TBC/EBCs can be deposited by atmospheric plasma spraying [149], while nitride, carbide, and oxide thin films can be prepared by reactive RF magnetron sputtering or DC sputtering of high-entropy alloys or co-sputtering of pure metal targets [150][151][152][153][154][155][156][157].…”

Section: Thin Films and Thick Coatingsmentioning

confidence: 99%

“…Combining simulations and experiments, they proposed a potential threshold for 5-metal carbides that could form single phase: EFA larger than 50 (eV/atom) -1 . In addition, by utilizing large configurational entropy, it is possible to stabilize the unstable phase to ambient conditions and improve the phase stability at high temperatures, as demonstrated in silicides, silicates, phosphates, niobates, and tantalates [33,71,88,92]. Besides configurational entropy, the phase stability of HECs could be affected by the size and charge of the constituent elements.…”

Section: Phase Stabilitymentioning

confidence: 99%

“…Intriguingly, the atomic size difference (δ) is one of the main factors that influence the formation of single phases in HEAs, where the threshold is 6.5% [29]. Nevertheless, in HECs, single phases are still observed in the systems with δ larger than 6.5% [71,76,88]. Jiang et al [76] proposed that the Goldschmidt tolerance factor (t) was a useful parameter in predicting the stability of high-entropy perovskites.…”

Section: Phase Stabilitymentioning

confidence: 99%

“…The complex composition, distorted lattice, and various bonding in HECs compared with single component systems lead to unexpected behavior of TECs. Experimentally, the average TEC can be probed by a high temperature push-rod dilatometer or an optical dilatometer [71,91,93], while the anisotropic TEC can be obtained from high-temperature powder XRD or high temperature push-rod dilatometer using single crystals [23,85,86,90,91]. Yan et al [35] measured the thermal expansion of (TiZrHfNbTa)C at 25-300 ℃, and the TEC of HE carbides did not show significant deviation from the binary carbides.…”

Section: Thermal Expansionmentioning

confidence: 99%

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High-entropy ceramics: Present status, challenges, and a look forward

et al. 2021

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High-entropy ceramics (HECs) are solid solutions of inorganic compounds with one or more Wyckoff sites shared by equal or near-equal atomic ratios of multi-principal elements. Although in the infant stage, the emerging of this new family of materials has brought new opportunities for material design and property tailoring. Distinct from metals, the diversity in crystal structure and electronic structure of ceramics provides huge space for properties tuning through band structure engineering and phonon engineering. Aside from strengthening, hardening, and low thermal conductivity that have already been found in high-entropy alloys, new properties like colossal dielectric constant, super ionic conductivity, severe anisotropic thermal expansion coefficient, strong electromagnetic wave absorption, etc., have been discovered in HECs. As a response to the rapid development in this nascent field, this article gives a comprehensive review on the structure features, theoretical methods for stability and property prediction, processing routes, novel properties, and prospective applications of HECs. The challenges on processing, characterization, and property predictions are also emphasized. Finally, future directions for new material exploration, novel processing, fundamental understanding, in-depth characterization, and database assessments are given.

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