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arXiv 2407.06388cond-mat.mtrl-scicond-mat.dis-nn
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高压合成条件对高熵氧化物形成的影响

Effect of high pressure synthesis conditions on the formation of high entropy oxides

Solveig Stubmo Aamlid, Minu Kim, Mario U. González-Rivas, Mohamed Oudah, Hidenori Takagi, Alannah M. Hallas

AI总结:

本文研究两类高熵氧化物在不同温度、压力和氧活度下的相平衡,发现高压可诱发尖晶石HEO形成新型亚稳相,并为制备常规条件无法获得的高熵相提供途径。

摘要:

高熵材料通常由熵稳定,这意味着多种元素共享单个晶格位点所产生的构型熵能够稳定其结构。在本研究中,我们考察高压合成条件如何稳定或失稳一种高熵氧化物(HEO)。我们研究了两类知名HEO的高压、高温相平衡:岩盐结构化合物(Mg,Co,Ni,Cu,Zn)O(包括部分阳离子取代)以及尖晶石结构(Cr,Mn,Fe,Co,Ni)₃O₄。合成在不同温度、压力和氧活度水平下进行,产生了显著不同的合成结果。特别是,在岩盐HEO中,我们观察到相互竞争的 tenorite(黑铜矿)相和纤锌矿相,以及可能形成层状岩盐相;而尖晶石HEO极易分解为岩盐相和刚玉相的混合物。在测试的最高压力15 GPa下,我们发现尖晶石HEO转变为一种亚稳态改性硼镁铁矿型结构,其名义化学式为(Cr,Mn,Fe,Co,Ni)₄O₅。合成条件与最终反应产物之间的关系并非简单直接。尽管如此,我们认为高压条件为合成无法通过其他方式形成的高熵相提供了重要机遇。

英文摘要:

High entropy materials are often entropy stabilized, meaning that the configurational entropy from multiple elements sharing a single lattice site stabilizes the structure. In this work, we study how high-pressure synthesis conditions can stabilize or destabilize a high entropy oxide (HEO). We study the high-pressure and high-temperature phase equilibria of two well-known families of HEOs: the rock-salt structured compound (Mg,Co,Ni,Cu,Zn)O including some cation substitutions and the spinel structured (Cr,Mn,Fe,Co,Ni)$_3$O$_4$. Syntheses were performed at various temperatures, pressures, and oxygen activity levels resulting in dramatically different synthesis outcomes. In particular, in the rock salt HEO we observe the competing tenorite and wurtzite phases and the possible formation of a layered rock salt phase, while the spinel HEO is highly susceptible to decomposition into a mixture of rock-salt and corundum phases. At the highest tested pressures, 15 GPa, we discover the transformation of the spinel HEO into a metastable modified ludwigite-type structure with nominal formula (Cr,Mn,Fe,Co,Ni)$_4$O$_5$. The relationship between the synthesis conditions and the final reaction product is not straightforward. Nonetheless, we conclude that high-pressure conditions provide an important opportunity to synthesize high entropy phases that cannot be formed any other way.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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