Synthesis and structures of high-entropy pyrochlore oxides

Teng, Zhen; Zhu, Lini; Tan, Yongqiang; Zeng, Shuai; Xia, Yuanhua; Wang, Yiguang; Zhang, Haibin

doi:10.1016/j.jeurceramsoc.2019.12.008

Cited by 157 publications

(53 citation statements)

References 34 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%

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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Section: Electronic Structure and Band Gap Engineeringmentioning

confidence: 99%

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

et al. 2021

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“…S3) revealed that the RE elements and ruthenium were uniformly distributed throughout the particle, indicating the successful synthesis of pyrochlore oxides. between the RE-and Ru-site, and the other connects to only the RE-site cations in the form of RE−O'−RE [31].…”

Section: Resultsmentioning

confidence: 99%

Rare-earth-regulated Ru-O interaction within the pyrochlore ruthenate for electrocatalytic oxygen evolution in acidic media

Liu

Wang

et al. 2021

Sci. China Mater.

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Ruthenium-based catalyst is one of the most active catalysts for oxygen evolution reaction (OER) in acid media. However, the strong bonding between the Ru sites and oxygen intermediates leads to high overpotential to trigger the OER process. Hence, pyrochlore rare-earth ruthenate (RE 2-Ru 2 O 7) structures with a series of rare-earth elements (Nd, Sm, Gd, Er, and Yb) were constructed to tune the electronic structure of the Ru sites. Surface structure analysis indicated that the increase of the radius of the rare-earth cations resulted in higher content of defective oxygen (the percentage of the defective oxygen increased from 29.5% to 49.7%) in the RE 2 Ru 2 O 7 structure due to the weakened hybridization of the Ru-O bond. This reduced the valence states of the Ru sites and enlarged the gap between the 4d band center and the Fermi level (E F) of Ru, resulting in the weakened adsorption of oxygen intermediates and the improved OER performance in acid media. Among the as-prepared ruthenium pyrochlores, Nd 2 Ru 2 O 7 displayed the lowest OER onset overpotential (210 mV) and Tafel slope (58.48 mV dec −1), as well as 30 times higher intrinsic activity and much higher durability than the state-of-art RuO 2 catalyst.

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“…01-071-2363). Notably, the peaks marked with black peach for the LZ1 were characteristic superlattice diffraction peaks of pyrochlore structure [25].…”

Section: Resultsmentioning

confidence: 99%

Synthesis and characterization of novel porous La2Zr2O7 ceramic with ultralow thermal conductivity and excellent photocatalytic property

Liu

Geng³

et al. 2021

Preprint

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A novel porous La2Zr2O7 ceramic prepared by combining a sol-gel template method and high-temperature calcination process. The structural evolution and crystallisation behaviour of the samples were systematically characterized using SEM, XRD, TEM and Raman spectroscopy. The results indicated that the as-prepared porous La2Zr2O7 ceramic had a typical nanoparticles assembling and mesoporous structure with single-phase pyrochlore crystal structure. Meanwhile, the as-prepared porous La2Zr2O7 ceramic presented an ultralow room temperature thermal conductivity of 0.07 W/(m·K), high specific surface areas of 325.17 m2/g and a relatively high compressive strength of 11.95 MPa. What’s more, the as-prepared porous La2Zr2O7 ceramic possessed ideal photocatalytic activity owing to the unique 3-D porous structure, high crystallinity and large surface area. These reported studies are proposing some new insight to improve porous rare-earth zirconates ceramic for thermal insulation and dye degradation applications.

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Synthesis and structures of high-entropy pyrochlore oxides

Cited by 157 publications

References 34 publications

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

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

Rare-earth-regulated Ru-O interaction within the pyrochlore ruthenate for electrocatalytic oxygen evolution in acidic media

Synthesis and characterization of novel porous La2Zr2O7 ceramic with ultralow thermal conductivity and excellent photocatalytic property

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