21-Component compositionally complex ceramics: Discovery of ultrahigh-entropy weberite and fergusonite phases and a pyrochlore-weberite transition
21-Component compositionally complex ceramics: Discovery of ultrahigh-entropy weberite and fergusonite phases and a pyrochlore-weberite transition
复制标题
DOI：
10.1007/s40145-022-0575-5
复制
发表时间：
2021-12
影响因子：
16.9
通讯作者：
Mingde Qin;Heidy Vega;Dawei Zhang;S. Adapa;Andrew J. Wright;Renkun Chen;Jian Luo
中科院分区：
文献类型：
--
作者：
Mingde Qin;Heidy Vega;Dawei Zhang;S. Adapa;Andrew J. Wright;Renkun Chen;Jian Luo
在21组分的氧化物体系中，发现了两种新的高熵陶瓷(HECS)，它们分别位于韦伯利石和辉铜矿结构中，并意外地形成了具有超高熵组成的有序焦绿石相，并发生了焦绿石-韦氏石的突变。虽然吉布斯相规则允许21个平衡相，但在所考察的13个组分中，有9个组分具有单一的HEC相(具有超高的理想构型熵：在大多数情况下，在一个亚晶格上每个阳离子的∼为2.7kB或更高)。值得注意的是，(15RE1/15)(Nb1/2Ta1/2)O4具有单一的单斜方闪锌矿(C2/c)相，并且(15RE1/15)3(Nb1/2Ta1/2)1O7形成单一的正交(C2221)韦伯利石相，其中15RE1/15表示Sc1/15Y1/15La1/15Pr1/15Nd1/15Sm1/15Eu1/15Gd1/15Tb1/15Dy1/15Ho1/15Er1/15Tm1/15Yb1/15Lu1/15.。此外，一系列八个(15RE1/15)2+x(Ti1/4Zr1/4Ce1/4H1/4)2−2x(Nb1/2Ta1/2)xO7specimens都表现为单相，在0.75<范围内发生烧绿石-韦伯利石转变；X<；0.8125。这种从立方到正交相的转变不会显著地改变随温度变化的热导率，因为在超高熵21组分的氧化物中可能已经达到了非晶态的极限。这些发现扩展了HECS的多样性和复杂性，向多组分组成复杂陶瓷(CCCS)和超高熵陶瓷发展。
Two new high-entropy ceramics (HECs) in the weberite and fergusonite structures, along with the unexpected formation of ordered pyrochlore phases with ultrahigh-entropy compositions and an abrupt pyrochlore-weberite transition, are discovered in a 21-component oxide system. While the Gibbs phase rule allows 21 equilibrium phases, 9 out of the 13 compositions examined possess single HEC phases (with ultrahigh ideal configurational entropies: ∼2.7kBper cation or higher on one sublattice in most cases). Notably, (15RE1/15)(Nb1/2Ta1/2)O4possess a single monoclinic fergusonite (C2/c) phase, and (15RE1/15)3(Nb1/2Ta1/2)1O7form a single orthorhombic (C2221) weberite phase, where 15RE1/15represents Sc1/15Y1/15La1/15Pr1/15Nd1/15Sm1/15Eu1/15Gd1/15Tb1/15Dy1/15Ho1/15Er1/15Tm1/15Yb1/15Lu1/15. Moreover, a series of eight (15RE1/15)2+x(Ti1/4Zr1/4Ce1/4H1/4)2−2x(Nb1/2Ta1/2)xO7specimens all exhibit single phases, where a pyrochlore-weberite transition occurs within 0.75 <x< 0.8125. This cubic-to-orthorhombic transition does not change the temperature-dependent thermal conductivity appreciably, as the amorphous limit may have already been achieved in the ultrahigh-entropy 21-component oxides. These discoveries expand the diversity and complexity of HECs, towards many-component compositionally complex ceramics (CCCs) and ultrahigh-entropy ceramics.