Novel electronic and magnetic properties of high Entropy Oxides

高熵氧化物的新颖电子和磁性特性

• 批准号: 431403378
• 负责人: Professor Dr. Hidenori Takagi
• 金额: --
• 依托单位: Max-Planck-Institut für Festkörperforschung (MPI-FKF)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/431403378?language=en
• 关键词: Novel; electronic; magnetic; properties; Entropy

This project is devoted to explore novel high-entropy oxides (HEOx) with exotic electronic and magnetic properties. HEOx is a novel class of materials discovered recently (C. M. Rost et al, Nat. Commun. 2015), by extending to oxides the concept of high-entropy materials that is well-known for metallic alloys. They comprise at least five different cations and are obtained by heating at high temperature and subsequent quenching. When the temperature is large enough, the entropy of configuration becomes dominant in the Gibbs energy, which drives the formation of a metastable solid-solution instead of enthalpy driven phases. Such entropy-stabilized oxides can be frozen at room temperature by quenching. The first synthesized HEOx, (MgCoNiCuZn)O, has a simple rocksalt structure. Interestingly, some of the constituting binary oxides do not crystallize in the rocksalt structure and even do not form solid solutions. Other types of HEOx with perovskite and spinel structures have been reported, suggesting a huge variety of materials to be explored. Unfavorable cationic dopants such as Zn2+ in an octahedral site may be able to be introduced in the HEOx. These make HEOx quite promising in the development of new oxide materials. We will explore new HEOx with perovskite, pyrochlore, spinel and related structures in this project.HEOx serve not only as a mine of materials but also as a mine of unexpected functionalities, partly due to the local lattice distortions with unconventional cation arrangement. In the rocksalt-type HEOx, we have discovered unexpected functions such as a colossal dielectric response, a high ion mobility over 1 mS/cm for lithium and a long-range antiferromagnetic ordering. Such novel properties and functions should not be limited in the rocksalt HEOx. By introducing the concept to correlated electrons in transition-metal oxides, unprecedented electronic and magnetic properties can be anticipated. The correlated transition metal oxides often host competing electronic states and the unique ground state is selected from them with the help of subtle lattice distortion. In HEOx-type correlated oxides, the structural disorder may not allow the system to choose its ground state, leading to exotic fluctuating phases and functionalities. The expected phases/functions include a giant magnetoelectric effect, a high-performance thermoelectricity and an exotic magnetism such as a quantum spin-liquid, which will be the targets of this project.Through the collaboration of two teams, the pioneer of entropy-stabilized materials (the French partner) and the leading group in correlated electron physics (the German partner), we aim to open a new arena in the research on electronic and functional oxides.

该项目致力于探索具有奇异电子和磁性的新型高熵氧化物（HEOx）。HEOx是最近发现的一类新材料（C. M. Rost等人，Nat.Commun. 2015），通过将金属合金中众所周知的高熵材料的概念扩展到氧化物。它们包含至少五种不同的阳离子，并通过在高温下加热和随后的淬火而获得。当温度足够高时，组态熵在吉布斯自由能中占主导地位，从而驱动亚稳固溶体的形成，而不是焓驱动相。这种熵稳定的氧化物可以通过淬火在室温下冷冻。 第一个合成的HEOx，（MgCoNiCuZn）O，具有简单的岩盐结构。有趣的是，一些组成的二元氧化物在岩盐结构中不结晶，甚至不形成固溶体。已经报道了具有钙钛矿和尖晶石结构的其他类型的HEOx，这表明有待探索的材料种类繁多。不利的阳离子掺杂剂如八面体位点中的Zn 2+可能能够被引入HEOx中。 这使得HEOx在开发新的氧化物材料方面非常有前途。在这个项目中，我们将探索具有钙钛矿、烧绿石、尖晶石和相关结构的新HEOx。HEOx不仅是一个材料矿，也是一个意想不到的功能矿，部分原因是非常规阳离子排列的局部晶格畸变。在岩盐型HEOx中，我们发现了意想不到的功能，如巨大的介电响应，锂离子迁移率超过1 mS/cm，以及长程反铁磁有序。这种新的性质和功能不应局限于岩盐HEOx。通过在过渡金属氧化物中引入相关电子的概念，可以预期前所未有的电子和磁性。相关的过渡金属氧化物通常具有竞争的电子态，并且借助于微妙的晶格畸变从它们中选择唯一的基态。在HEOx型相关氧化物中，结构无序可能不允许系统选择其基态，导致奇异的波动相和功能。 预期的相/功能包括巨磁电效应，高性能热电和奇异磁性，如量子自旋液体，这将是该项目的目标。通过两个团队的合作，熵稳定材料的先驱（法国合作伙伴）和相关电子物理学领导小组（德国合作伙伴），我们的目标是在电子和功能氧化物的研究中开辟一个新的竞技场。