High-Pressure Synthesis and Physical Properties of New Oxides with Perovskite or Perovskite-Related Structure

具有钙钛矿或钙钛矿相关结构的新型氧化物的高压合成及其物理性质技术摘要：具有钙钛矿或钙钛矿相关结构的4d和5d过渡金属氧化物的轨道角动量未猝灭导致了新型Mott绝缘体和异常金属相。由于强自旋-轨道耦合，它们的奇异物理性质近年来引起了广泛的关注。钙钛矿中的a位阳离子对费米能附近的电子态没有直接贡献。然而，在高tc铜酸盐和磁阻锰酸盐中，超导转变温度、磁转变温度和磁化强度对a -阳离子无序度和平均a -阳离子尺寸高度敏感。a -阳离子对4d和5d过渡金属氧化物物理性质的影响还没有系统的研究。a -阳离子尺寸方差的引入和a -阳离子平均尺寸在大范围内的变化通常受到环境压力下几何容差系数的限制。要完成这一课题的研究，在某些情况下需要在高达P ~ 20gpa的压力下进行合成。在地球科学领域，已发展了p20gpa大体积高压合成技术来研究地球？S下地幔。然而，在大范围的固态合成中，它仍然是一个未开发的领域，无法施加超过10 GPa的压力。这笔资金将使pi不仅能够解决具有未淬灭轨道角动量的4d和5d金属氧化物物理性质的关键因素，而且还可以在20gpa压力下系统地探索固态合成。非技术概述：钙钛矿氧化物是技术上重要的材料，广泛应用于微电子工业，在化工厂中作为催化剂，在固态燃料电池中作为电解质和电极。本项目概述的基础研究将有助于更好地了解钙钛矿氧化物，从而极大地促进其应用。pi有什么独特之处？实验室是他们已经建立了一些复杂的仪器材料合成，表征和测量，他们有很长的历史强调晶体结构，化学，他们的物理性质和他们的工程应用之间的关系。实验结果与理论计算结果直接比较。项目pi强调高压合成和晶体生长。这些特点吸引了世界各地的学者来到这个实验室。具有不同材料科学、化学和物理背景的学生、博士后和访问学者有机会相互交流，并在研究项目的同时制定自己的材料研究策略。访问研究人员也带来了他们在本国实验室发展的专长。所有这些因素创造了一个非常丰富的学习和研究环境。在这个项目中，pi还与西班牙、日本、中国和加拿大的科学家合作。

DMR 0904282High-pressure synthesis and physical properties of new oxides with perovskite or perovskite-related structureTECHNICAL SUMMARY:Unquenched orbital angular momentum in the 4d and 5d transition-metal oxides with the perovskite or the perovskite-related structure leads to a new type of Mott insulator and anomalous metallic phases. Their exotic physical properties due to strong spin-orbit coupling have attracted broad attention in recent years. The A-site cation in these perovskites does not contribute directly to the electronic states near the Fermi energy. However, as shown in high-Tc cuprates and the magnetoresistive manganites, superconductive transition temperature, the magnetic transition temperature, and the magnetization are highly sensitive to the A-cation disorder as well as the mean A-cation size. The A-cation effect on the physical properties of the 4d and 5d transition-metal oxides has not been studied systematically. Introduction of A-cation size variance and the change of mean A-cation size in a wide range is normally limited by the geometric tolerance factor at ambient pressure. A complete study of this subject requires synthesis at pressures as high as P ~ 20 GPa in some cases. The high-pressure synthesis with a large volume at P 20 GPa has been developed in the field of geoscience to study the earth?s lower mantle. However, it remains essentially a virgin field to apply pressure over 10 GPa in a broad range of solid-state synthesis. This funding will allow the PIs not only to address key factors determining physical properties in the 4d and 5d metal oxides with unquenched orbital angular momentum, but also to explore systematically solid-state synthesis under pressure to 20 GPa. NON-TECHINICAL SUMMARY:Perovskite oxides are technically important materials that are widely used in the microelectronic industry, in chemical plants as catalysts, and in solid-state fuel cells as both electrolyte and electrodes. The basic research outlined in this project will lead to a better understanding of perovskite oxides, which in turn benefits greatly their application. What is unique about the PIs? laboratory is that they have established several sophisticated instruments for material synthesis, characterization, and measurements and they have a long history of emphasis on the relationship between crystal structures, chemistry, their physical properties, and their engineering application. Experimental results are compared directly with theoretical calculations. The PIs emphasize high-pressure synthesis and crystal growth in the project. These characteristics have attracted scholars around the world to the laboratory. Students, post-docs, and visiting scholars with diversified backgrounds of materials science, chemistry and physics have a chance to interact with each other and to develop their own strategy of material research while working on the project. Visiting researchers have also brought with their specialties developed in their home laboratories. All these factors create a very rich environment for learning and research. In this project, the PIs also collaborate with scientists in Spain, Japan, China and Canada.