High-entropy rare earth tetraborides

Qin, Mingde; Yan, Qizhang; Wang, Haoren; Vecchio, Kenneth S.; Luo, Jian

doi:10.1016/j.jeurceramsoc.2020.12.019

Cited by 37 publications

(6 citation statements)

References 48 publications

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“…It is even more difficult to predict GB properties (and subsequently compute GB diagrams) for the diversifying classes of high-entropy ceramics (HECs) [66,67] and compositionally complex ceramics (CCCs), [66,[169][170][171][172], which have attracted substantial and exponentially growing research interests recently. GBs in high-entropy (and compositionally complex) oxides, [66,169,[172][173][174][175] borides, [176][177][178][179] carbides, [180][181][182] silicides, [183,184] and fluorides [185] with diversifying crystal structures and different bonding characters can possess exotic yet intriguing F I G U R E 15 Computing GB diagrams of thermodynamic and mechanical properties for Ga-doped Al. [64] (A) Validation of the computational approach by comparing an experimental STEM HAADF image with a simulated STEM image of an asymmetric Σ81 GB that best matches the experiment, based on the equilibrium atomistic structure obtained from hybrid MC/MD simulations.…”

Section: Discussionmentioning

confidence: 99%

“…It is even more difficult to predict GB properties (and subsequently compute GB diagrams) for the diversifying classes of high‐entropy ceramics (HECs) [ 66,67 ] and compositionally complex ceramics (CCCs), [ 66,169–172 ], which have attracted substantial and exponentially growing research interests recently. GBs in high‐entropy (and compositionally complex) oxides, [ 66,169,172–175 ] borides, [ 176–179 ] carbides, [ 180–182 ] silicides, [ 183,184 ] and fluorides [ 185 ] with diversifying crystal structures and different bonding characters can possess exotic yet intriguing thermodynamic and other physical properties. Understanding, predicting, and controlling the GBs in HEAs/CCCs and HECs/CCCs are of critical importance to enable us to attain their full technological potential.…”

Section: Discussionmentioning

confidence: 99%

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Computing grain boundary “phase” diagrams

Luo

2023

Interdisciplinary Materials

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Grain boundaries (GBs) can be treated as two‐dimensional (2‐D) interfacial phases (also called “complexions”) that can undergo interfacial phase‐like transitions. As bulk phase diagrams and calculation of phase diagram (CALPHAD) methods serve as a foundation for modern materials science, we propose to extend them to GBs to have equally significant impacts. This perspective article reviews a series of studies to compute the GB counterparts to bulk phase diagrams. First, a phenomenological interfacial thermodynamic model was developed to construct GB lambda diagrams to forecast high‐temperature GB disordering and related trends in sintering and other properties for both metallic and ceramic materials. In parallel, an Ising‐type lattice statistical thermodynamic model was utilized to construct GB adsorption (segregation) diagrams, which predicted first‐order GB adsorption transitions and critical phenomena. These two simplified thermodynamic models emphasize the GB structural (disordering) and chemical (adsorption) aspects, respectively. Subsequently, hybrid Monte Carlo and molecular dynamics atomistic simulations were used to compute more rigorous and accurate GB “phase” diagrams. Computed GB diagrams of thermodynamic and structural properties were further extended to include mechanical properties. Moreover, machine learning algorithms were combined with atomistic simulations to predict GB properties as functions of four independent compositional variables and temperature in a 5‐D space for a given GB in high‐entropy alloys or as functions of five GB macroscopic (crystallographic) degrees of freedom plus temperature and composition for a binary alloy in a 7‐D space. Other relevant studies are also examined. Future perspective and outlook, including two emerging fields of high‐entropy grain boundaries (HEGBs) and electrically (or electrochemically) induced GB transitions, are discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Computing grain boundary “phase” diagrams

Luo

2023

Interdisciplinary Materials

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“…13c). 192 The UB 4 -prototype tetraboride unit cell could be interpreted as alternating MB 2 and MB 6 units. Along the c -axis, octahedra composed of six boron atoms are connected linearly.…”

Section: Other High-entropy Rare Earth Ceramicsmentioning

confidence: 99%

“…Simultaneously, it has expanded to other compounds such as HE-RE transition metal oxides with perovskite, 35 spinel, 36 and garnet 37 structures, HE-RE silicates, 38 aluminates, 39 and borides. 40 Furthermore, due to the significance of RE ceramics in the traditional ceramics field, there has been substantial research and understanding in this area. 41 Therefore, the study of HE-RE ceramics is guided by the optimization of the performance for each category of traditional RE ceramics, making their research development highly traceable.…”

Section: Chunhua Yanmentioning

confidence: 99%

High-entropy rare earth materials: synthesis, application and outlook

Fu,

Jiang,

Zhang

et al. 2024

Chem. Soc. Rev.

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“…Following the metallic high-entropy alloys (HEAs) which have been extensively studied since 2004 [1,2], high-entropy ceramics including oxides [3][4][5][6][7][8][9][10], borides [11][12][13][14][15], carbides [16][17][18][19], and silicides [20,21] have been developed and studied intensively in recent years. High-entropy ceramics generally exhibit special physical and chemical properties, which are generally resulted from their complex composition, severe lattice distortion, and the sluggish diffusion effect [22][23][24].…”

Section: Introduction mentioning

confidence: 99%

Fast grain growth phenomenon in high-entropy ceramics: A case study in rare-earth hexaaluminates

Zhou¹,

LIU²,

Tianzhe³

et al. 2023

Journal of Advanced Ceramics

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It is generally reported that the grain growth in high-entropy ceramics at high temperatures is relatively slower than that in the corresponding single-component ceramics owing to the so-called sluggish diffusion effect. In this study, we report a fast grain growth phenomenon in the high-entropy ceramics (La 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 )MgAl 11 O 19 (HEMA) prepared by a conventional solid-state reaction method. The results demonstrate that the grain sizes of the as-sintered HEMA ceramics are larger than those of the corresponding five single-component ceramics prepared by the same pressureless sintering process, and the grain growth rate of HEMA ceramics is obviously higher than those of the five single-component ceramics during the subsequent heat treatment. Such fast grain growth phenomenon indicates that the sluggish diffusion effect cannot dominate the grain growth behavior of the current high-entropy ceramics. The X-ray photoelectron spectroscopy (XPS) analysis reveals that there are more oxygen vacancies (O V ) in the high-entropy ceramics than those in the single-component ceramics owing to the variable valance states of Eu ion. The high-temperature electrical conductivities of the HEMA ceramics support this analysis. It is considered that the high concentration of O V and its high mobility in HEMA ceramics contribute to the accelerated migration and diffusion of cations and consequently increase the grain growth rate. Based on this study, it is believed that multiple intrinsic factors for the high-entropy ceramic system will simultaneously determine the grain growth behavior at high temperatures.

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High-entropy rare earth tetraborides

Cited by 37 publications

References 48 publications

Computing grain boundary “phase” diagrams

Computing grain boundary “phase” diagrams

High-entropy rare earth materials: synthesis, application and outlook

Fast grain growth phenomenon in high-entropy ceramics: A case study in rare-earth hexaaluminates

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