Point Defects in Intermetallics using PAC

使用 PAC 测量金属间化合物中的点缺陷

• 批准号: 0091681
• 负责人: Gary Collins
• 金额: --
• 依托单位: Washington State University
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-02-01 至 2005-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0091681&HistoricalAwards=false
• 关键词: Point; Defects; Intermetallics; using; PAC

0091681 CollinsPoint defects in intermetallic compounds are studied using perturbed angular correlation of gamma rays (PAC). Local environments of dilute indium probe atoms are resolved through measurement of characteristic quadrupole interactions. Two kinds of environment are studied: probe atoms as solutes on inequivalent lattice sites in a compound or mixture of phases, and probes bound in complexes with lattice vacancies. Research is in three areas that are natural extensions of recent work. Preferences of solute atoms for different lattice sites in compounds or in two-phase alloys are determined through measurement of fractions of probe atoms in the different sites. Sublattice sites are identified by comparing measured quadrupole interactions with those in a series of compounds having the same structure and with computations of quadrupole interactions. The goal is to develop a more systematic understanding of site preferences. The effect of applied pressure on the quadrupole interactions of probes bound in complexes with lattice vacancies are studied at room temperature using a diamond anvil cell. The expectation is that there will be large relaxations of atoms near vacancy complexes. Pressure dependencies will be correlated with temperature dependencies and with computations of the structures and electric-field gradients of the complexes. The goal is to understand how the shape and volume of vacancy clusters change under the influence of pressure and temperature. Four processes involving point defects will be studied: defect formation, binding of vacancies to probe atoms, conversion between different structural point defects in non-stoichiometric compounds, and vacancy migration. Activation volumes for the first three processes will be determined through measurement of site fractions of probe-vacancy complexes. The activation volume for vacancy migration will be determined from the pressure dependence of signal relaxation caused by stochastic jumping of vacancies near probe atoms. %%%These measurements will provide fundamental information about point defect processes. These will be the first high pressure PAC studies carried out using a diamond anvil cell and the first at high temperature. Results in this area should be useful to researchers studying increasingly complex systems using PAC and similar methods.***

0091681科林斯点缺陷在金属间化合物中使用扰动角相关的γ射线（PAC）进行了研究。通过测量特征四极相互作用，解决了稀铟探针原子的局域环境。研究了两种环境：探针原子作为溶质在化合物或混合物中的不等价晶格位点上，以及探针与晶格空位结合在复合物中。研究是在三个领域，是最近的工作自然延伸。溶质原子在化合物或两相合金中对不同晶格位置的偏好是通过测量探针原子在不同位置的分数来确定的。通过比较测量的四极相互作用与具有相同结构的一系列化合物中的四极相互作用和四极相互作用的计算来确定子晶格位点。目标是更系统地了解网站偏好。用金刚石对顶砧装置研究了室温下压力对探针与晶格空位复合物的四极相互作用的影响。预期在空位复合物附近的原子将有大的弛豫。压力的依赖性将与温度的依赖性和计算的结构和电场梯度的复合物。我们的目标是了解在压力和温度的影响下，空位簇的形状和体积如何变化。涉及点缺陷的四个过程将被研究：缺陷的形成，结合的空缺探针原子，在非化学计量的化合物中的不同结构的点缺陷之间的转换，和空位迁移。前三个过程的活化体积将通过测量探针-空位复合物的位点分数来确定。空位迁移的激活体积将由探针原子附近空位的随机跳跃引起的信号弛豫的压力依赖性确定。这些测量将提供有关点缺陷过程的基本信息。这将是第一次使用金刚石对顶砧进行高压PAC研究，也是第一次在高温下进行高压PAC研究。这一领域的研究结果对研究人员使用PAC和类似方法研究日益复杂的系统应该是有用的。