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Study of elementary processes of diffusion in compound crystals of the L1_2 and E2_1 structures by anelastic

L1_2和E2_1结构复合晶体中滞弹性扩散基本过程研究

基本信息

批准号：
17560584
负责人：
NUMAKURA Hiroshi
金额：
$ 2.24万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

项目摘要

Several years ago we suggested that the mechanical relaxation effect observed in Ni_3A1 was caused by stress-induced diffusional jumps of anti-site Al atoms (occupying Ni atom sites), and since then we have pursued the problem by carrying out various experiments. In the first year of this investigation we examined the effect of deviation of composition from the stoichiometry (25 mol % Al) on the relaxation effect in Ni_3A1. We found that the relaxation rate did not depend on composition, but the relaxation strength was increased markedly as the composition exceeded the stoichiometry. These results are in excellent agreement with the predictions from the postulated mechanism.Experiments on Ni_3Ga were made in the second year, where a similar mechanical relaxation effect was discovered. The values of the relaxation rate and its temperature dependence indicate that the relaxation is due to anti-site Ga atoms. Assuming that the diffusion of Ga in Ni_3Ga occurs via the same mechanism as the diffusion of Al in Ni_3A1, we have evaluated the diffusion coefficient of Al in Ni_3Al and that of Ga in Ni_3Ga. The latter is close to the data in the literature, which were measured directly by radio-tracer experiments, indicating that the relaxation is in fact due to diffusion of anti-site Ga atoms. As a preparation for extending the study to another L1_2 compound Ir_3Nb, we have measured the chemical diffusion.Lastly, in order to measure the diffusion of oxygen ions in oxides of the E2_1 (cubic perovskite) structure by the same principle, we have prepared samples of (Ba, Sr)TiO_3. We will carry out experiments on these samples in due course.

几年前，我们提出在Ni_3A1中观察到的机械弛豫效应是由应力引起的反位Al原子（占据Ni原子位点）的扩散跳跃引起的，从那时起我们通过进行各种实验来解决这个问题。在这项研究的第一年，我们研究了成分与化学计量（25 mol% Al）的偏差对 Ni_3Al 弛豫效应的影响。我们发现松弛速率并不取决于成分，但当成分超过化学计量时，松弛强度显着增加。这些结果与假设机制的预测非常吻合。第二年对Ni_3Ga进行了实验，发现了类似的机械弛豫效应。弛豫率的值及其温度依赖性表明弛豫是由于反位 Ga 原子造成的。假设Ga在Ni_3Ga中的扩散与Al在Ni_3Al中的扩散具有相同的机制，我们评估了Al在Ni_3Al中的扩散系数和Ga在Ni_3Ga中的扩散系数。后者与文献中的数据接近，这些数据是通过放射性示踪剂实验直接测量的，表明弛豫实际上是由于反位Ga原子的扩散造成的。作为将研究扩展到另一种L1_2化合物Ir_3Nb的准备，我们测量了化学扩散。最后，为了通过相同的原理测量氧离子在E2_1（立方钙钛矿）结构的氧化物中的扩散，我们制备了（Ba，Sr）TiO_3样品。我们将适时对这些样品进行实验。