High-Pressure Synthesis and Physical Properties of New Perovskite Oxides with Stretched Bonding

该项目旨在系统地研究AMO 3钙钛矿中从局部到巡回电子行为的交叉处遇到的不寻常的物理性质，这些钙钛矿在M原子处只有p键3d或4d电子，具有/不具有t轨道简并性。 特别强调的是钙钛矿，具有拉伸的M-O键作为一个结果的大A-位点阳离子。 几乎所有这些氧化物都需要高压合成。 我们还将使用高压变量来微调交叉处和轨道或电荷有序/无序转变处的物理性质，其中在较低温度下发现量子临界点行为。 更广泛的影响包括将我们的高压设备升级到250 kbar的容量，这将允许解决材料设计的几个关键基本问题。 学生将接受高压技术的实践培训，并将为相关学科的年轻科学家和研究人员编写一本教科书，以更新广大观众对我们对结构，磁性，和运输过渡金属化合物的（电子和离子）性质。非技术性压力技术，以澄清的字符和不寻常的物理性质，遇到了从磁绝缘体到金属行为的临界交叉和过渡金属化合物中的电荷或轨道有序无序过渡的演变。 它还将使用高压来合成具有拉伸化学键的材料，这种现象与技术上重要的介电和铁电行为有关，其中d轨道是空的，但未探索它们被占据的地方。 例如，在磁绝缘体到金属的转变中遇到的典型的不寻常的物理性质是某些铜氧化物的高温超导性和在某些锰和钴氧化物中发现的巨磁阻现象。 这项工作的更广泛影响包括将我们的高压能力升级到250 GPa，这将使我们能够探索地球内部材料的特性，并增加材料科学研究的新能力。 此外，澄清研究中的不寻常的物理性质的起源将允许材料的设计表现出新的性能的技术利益。 这项工作还将训练学生掌握高压技术。 将为相关领域的年轻科学家和研究人员编写一本教科书。

TechnicalThis project aims to systematically investigate unusual physical properties encountered at the crossover from localized to itinerant electronic behavior in AMO3 perovskites having only p-bonding 3d or 4d electrons at the M atoms with/without a t-orbital degeneracy. Particular emphasis is placed on perovskites that have a stretched M-O bond as a result of large A-site cations. Almost all these oxides require high-pressure synthesis. We will also use the high-pressure variable to fine-tune physical properties at the crossover and at orbital or charge order/disorder transitions where quantum critical-point behavior is found at lower temperatures. Broader impacts include up-grading our high-pressure apparatus to a capacity of 250 kbar, which will allow solution of several critical fundamental problems for material design. Students will be given hands-on training in high-pressure techniques, and a text book for young scientists and researchers in related disciplines will be undertaken to up-date a broad audience on recent advances in our understanding of the structural, magnetic, and transport (electronic and ionic) properties of transition-metal compounds.Non-technicalThis proposal uses high-pressure techniques to clarify the character and evolution of unusual physical properties that are encountered at critical crossovers from magnet-insulator to metallic behavior and at charge or orbital order-disorder transitions in transition-metal compounds. It would also use high pressure to synthesize materials with stretched chemical bonds, a phenomenon associated with technically important dielectric and ferroelectric behavior where the d orbtials are empty, but unexplored where they are occupied. Typical of the unusual physical properties that are encountered at magnetic-insulator to metal transitions, for example, are the high-temperature superconductivity of some copper oxides and the colossal magnetoresistance phenomenon found in some manganese and cobalt oxides. The broader impact of the work includes an up-grading of our high-pressure capacity to 250 GPa, which will allow us to explore the properties of materials in the interior of the earth as well as to add new capability in the materials science research. In addition, clarification of the origins of the unusual physical properties under study will allow design of materials exhibiting new properties of technical interest. The work will also train students in high-pressure techniques. Writing of a textbook for younger scientist and researchers in related fields will be undertaken.