Resonant Ultrasound Studies of Complex Materials: Clathrates and Transition Metal Oxides

复杂材料的共振超声研究：包合物和过渡金属氧化物

• 批准号: 0506292
• 负责人: Veerle Keppens
• 金额: $ 31.5万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0506292&HistoricalAwards=false
• 关键词: Resonant; Ultrasound; Studies; Complex; Materials

*** NON-TECHNICAL ABSTRACT ***One of the most exciting themes of modern condensed matter physics is the discovery and investigation of novel phenomena and new forms of order in materials systems of ever increasing complexity. It is one of the goals of the proposed program to study the elastic properties (i.e., how a material responds to strain) of novel, complex materials. Two kinds of complex materials will be studied: transition metal oxides and so-called inclusion compounds (compounds with a cage-like structure). The latter are promising for the development of better thermoelectric devices, which convert heat to electricity (and vice-versa) without moving parts or chloroflurocarbon (CFC)-containing refrigerants. The elastic behavior of these complex materials can be quite exotic, and this research program will explore to what extent the behavior can be understood with recently developed theories. Both senior undergraduate and graduate students will gain in-depth experience in the field of elastic properties and low temperature physics, and will acquire skills in various techniques in materials science. This proposal includes the development of outreach activities to undergraduate students in the department. Special efforts will be made to reach female students.*** TECHNICAL ABSTRACT ***This research program is designed to systematically study the elastic response of complex materials, including transition metal oxides (TMOs) and inclusion compounds. The materials that will be investigated are at the forefront of condensed matter physics and include the layered perovskite ruthenates Ca_(2-x)Sr_(x)RuO_(4), the triangular lattice compound Na_(x)CoO_(2), and inclusion compounds such as YbFe_(4)Sb_(12) and type-II clathrates such as Rb_(8)Na_(16)Si_(136). Resonant Ultrasound Spectroscopy will be routinely used from 2-400 K to obtain the elastic moduli. Pulse-echo and attenuation measurements in a He3-cryostat will be performed as appropriate. Scientifically, there are a number of issues that need to be resolved. One issue involves the relationship between inclusion compounds and structural glasses. Specifically, are tunneling states intrinsic to inclusion compounds? If so, can the tunneling entities be identified? Another issue involves structure-property relationships. To what extent can various structural features be used to predict the properties of the material? Can the elastic properties of TMOs be understood with recently developed ideas involving geometric and other types of frustration, nano-scale phase separation, and quantum-criticality? Both senior undergraduate and graduate students will gain in-depth experience in the field of elastic properties and low temperature physics, and will acquire skills in various techniques in materials science. This proposal includes the development of outreach activities to undergraduate students in the department. Special efforts will be made to reach female students.

*非技术摘要*现代凝聚态物理学最令人兴奋的主题之一是发现和研究日益复杂的材料系统中的新现象和新秩序形式。研究新型复杂材料的弹性性质(即材料对应变的响应)是拟议计划的目标之一。将研究两种复杂材料：过渡金属氧化物和所谓的包合物(具有笼状结构的化合物)。后者有望开发出更好的热电设备，将热能转化为电能(反之亦然)，而无需移动部件或含氯氟烃(CFC)的制冷剂。这些复杂材料的弹性行为可能是相当奇怪的，这个研究计划将探索最近发展的理论在多大程度上可以理解这种行为。高年级本科生和研究生都将在弹性性质和低温物理领域获得深入的经验，并将获得材料科学中各种技术的技能。这项提议包括开展面向系本科生的外联活动。这个研究项目旨在系统地研究复杂材料的弹性响应，包括过渡金属氧化物(TMO)和夹杂化合物。将要研究的材料处于凝聚态物理的前沿，包括层状钙钛矿型RuO4，三角形晶格化合物NaxCoO2，包裹体化合物如YbFe4Sb12和II型包合物如Rb8Na16Si136。在2-400K温度范围内，通常使用共振超声频谱技术来获得弹性模数。将适当地在HE3-低温恒温器中进行脉冲回波和衰减测量。从科学上讲，有许多问题需要解决。其中一个问题涉及包合物和结构玻璃之间的关系。具体地说，隧道态是包合物固有的吗？如果是，能否识别隧道实体？另一个问题涉及结构-财产关系。可以在多大程度上使用各种结构特征来预测材料的性能？用最近发展起来的涉及几何和其他类型的挫折、纳米级相分离和量子临界性的概念来理解TMO的弹性性质吗？高年级本科生和研究生都将在弹性性质和低温物理领域获得深入的经验，并将获得材料科学中各种技术的技能。这项提议包括开展面向系本科生的外联活动。将特别努力接触到女学生。