A high entropy silicide by reactive spark plasma sintering

Qin, Yuan; Liu, Jixuan; Li, Fēi; Wei, Xiaofeng; Wu, Houzheng; Zhang, Guojun

doi:10.1007/s40145-019-0319-3

Cited by 235 publications

(129 citation statements)

References 33 publications

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“…Since 2015, high-entropy ceramics (HECs) have been made in bulk form, including various high-entropy oxides [6][7][8][9][10], borides [11,12], carbides [13][14][15], nitrides [16], and silicides [17,18]. Unlike metallic HEAs of simple FCC, BCC or HCP structures, HECs typically only have high-entropy mixing at one (or multiple) cation sublattice(s).…”

Section: Introductionmentioning

confidence: 99%

From high-entropy ceramics to compositionally-complex ceramics: A case study of fluorite oxides

Wright

Wang

Huang

et al. 2020

Journal of the European Ceramic Society

207

125

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Using fluorite oxides as an example, this study broadens high-entropy ceramics (HECs) to compositionally-complex ceramics (CCCs) or multi-principal cation ceramics (MPCCs) to include medium-entropy and/or non-equimolar compositions. Nine compositions of compositionally-complex fluorite oxides (CCFOs) with the general formula of (Hf1/3Zr1/3Ce1/3)1x(Y1/2X1/2)xO2-δ (X = Yb, Ca, and Gd; x = 0.4, 0.148, and 0.058) are fabricated. The phase stability, mechanical properties, and thermal conductivities are measured. Compared with yttriastabilized zirconia, these CCFOs exhibit increased cubic phase stability and reduced thermal conductivity, while retaining high Young's modulus (~210 GPa) and nanohardness (~18 GPa).Moreover, the temperature-dependent thermal conductivity in the non-equimolar CCFOs shows an amorphous-like behavior. In comparison with their equimolar high-entropy counterparts, the medium-entropy non-equimolar CCFOs exhibit even lower thermal conductivity (k) while maintaining high modulus (E), thereby achieving higher E/k ratios. These results suggest a new direction to achieve thermally-insulative yet stiff CCCs (MPCCs) via exploring non-equimolar and/or medium-entropy compositions. Summary of Novel Conclusions:This study broadens "high-entropy ceramics" to "compositionally-complex ceramics". Using fluorite oxides as an example, we show that lower thermal conductivity and higher stiffness-toconductivity ratios are achieved in medium-entropy non-equimolar compositions. Highlights:• Nine compositionally-complex fluorite oxides (CCFOs) are made and investigated.• CCFOs exhibit reduced thermal conductivity and increased cubic phase stability.• Lower thermal conductivity is achieved in medium-entropy non-equimolar CCFOs.• High modulus and hardness retain in CCFOs with reduced thermal conductivity.• Non-equimolar CCFOs exhibit amorphous-like T-dependent thermal conductivity.

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Section: Introductionmentioning

confidence: 99%

From high-entropy ceramics to compositionally-complex ceramics: A case study of fluorite oxides

Wright

Wang

Huang

et al. 2020

Journal of the European Ceramic Society

207

125

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“…There are four core effects, namely high-entropy, severe lattice distortion, sluggish diffusion, and cocktail effects, in high-entropy materials that may affect their microstructure and properties [13]. High-entropy oxides [12], carbides [14,15], borides [16], and silicides [17,18] with rock salt structures or simple hexagonal structures and with fascinating properties have been produced by solid-state reactions and high temperature sintering. As for oxide ceramics, single-phase high-entropy rock salt (AO) [12], fluorite (AO 2 ) [19], perovskite (ABO 3 ) [20], and spinel (AB 2 O 4 ) [21] structures, where A and B are metallic elements, have been established.…”

Section: Introductionmentioning

confidence: 99%

High-entropy pyrochlores with low thermal conductivity for thermal barrier coating materials

et al. 2019

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High-entropy pyrochlore-type structures based on rare-earth zirconates are successfully produced by conventional solid-state reaction method. Six rare-earth oxides (are used as the raw powders. Five out of the six rare-earth oxides with equimolar ratio and ZrO 2 are mixed and sintered at different temperatures for investigating the reaction process. The results demonstrate that the high-entropy pyrochlores (5RE 1/5 ) 2 Zr 2 O 7 have been formed after heated at 1000 ℃. The (5RE 1/5 ) 2 Zr 2 O 7 are highly sintering resistant and possess excellent thermal stability. The thermal conductivities of the (5RE 1/5 ) 2 Zr 2 O 7 high-entropy ceramics are below 1 W·m -1 ·K -1 in the temperature range of 300-1200 ℃. The (5RE 1/5 ) 2 Zr 2 O 7 can be potential thermal barrier coating materials.

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“…In addition to two major classes high-entropy UHTCs (discussed above) that have been extensively studied in the last a few years, high-entropy nitrides [67], silicides [44,45], sulfides [98], fluorides [99], aluminides [43], hexaborides [100], carbonitrides [101], and aluminosilicides [38] have been fabricated. In the broader families of oxide-related HECs, the fabrication of high-entropy magnetoplumbites [87,102], zeolitic imidazolate frameworks [103], ferrites [104], phosphates [18,105], monosilicates [19,20], disilicates [106], and metal oxide nanotube arrays [107] have been reported.…”

Section: Graphical Abstractmentioning

confidence: 99%

“…The high-entropy borides and carbides are being examined for their potential use as nextgeneration UHTCs [118,119]. These classes of materials have also shown increased mechanical properties [56,61,62,64,66] and oxidation resistance [48,63,120,121] Notably, a general property of HECs is represented by the increased hardness in comparison with the RoM averages, which have been reported for high-entropy borides [48,50,54,56], carbides [59,61,63,66], and silicides [44,45]. Further discussion can be found in the next section.…”

Section: Propertiesmentioning

confidence: 99%

A step forward from high-entropy ceramics to compositionally complex ceramics: a new perspective

2020

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High-entropy ceramics (HECs) have quickly gained attention since 2015. To date, nearly all work has focused on five-component, equimolar compositions. This perspective article briefly reviews different families of HECs and selected properties. Following a couple of our most recent studies, we propose a step forward to expand HECs to Compositionally Complex ceramics (CCCs) to include medium-entropy and non-equimolar compositions. Using defective fluorite and ordered pyrochlore oxides as two primary examples, we further consider the complexities of aliovalent cations and anion vacancies as well as ordered structures with two cation sublattices.Better thermally-insulating yet stiff CCCs have been found in non-equimolar compositions with optimal amounts of oxygen vacancies and in ordered pyrochlores with substantial size disorder.It is demonstrated that medium-entropy ceramics (MECs) can prevail over their high-entropy counterparts. The diversifying classes of CCCs provide even more possibilities than HECs to tailor the composition, defects, disorder/order, and, consequently, various properties.

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A high entropy silicide by reactive spark plasma sintering

Cited by 235 publications

References 33 publications

From high-entropy ceramics to compositionally-complex ceramics: A case study of fluorite oxides

From high-entropy ceramics to compositionally-complex ceramics: A case study of fluorite oxides

High-entropy pyrochlores with low thermal conductivity for thermal barrier coating materials

A step forward from high-entropy ceramics to compositionally complex ceramics: a new perspective

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