Methods for Determining Migration Properties of Point Defects in Metal Oxides

该项目的目的是通过在高压电子显微镜中观察辐照过程中的缺陷聚集，找出确定金属氧化物中点缺陷迁移特性的方法。本文对MgO、Mg中位错环动力学和点缺陷迁移能进行了研究<Al_2><O_3><Al_2><O_4>。MgO<C_L>中的环的体积密度和直径D对于MgO作为电子通量<phi>、辐照时间t和辐照温度T的函数示出，对于T&lt;900 K，为<C_L><proportion>&lt;phi^（1/2）&gt; &lt;t^θ&gt; /（<M_I>）&lt;^（1/2）&gt;和D <proportion>&lt;t^（1/3）&gt;，对于T&gt; 900 K，为D &lt;phi^（1/2）&gt;<M_U>，其中<M_I>和<M_U>分别是材料和空位的迁移率。对和D的实验结果<C_L>给出了较低间隙原子和空位的迁移能分别为0.05 eV和2.0 eV.含<C_L>空穴时，和D对<phi>和t<Al_2>的依赖关系<O_3>表示为<C_L><proportion>&lt;phi^2&gt; t/<M_I>&lt;Cu_O^2&gt;和D <phi>t/<Cu_O>，其中<Cv_O>D t/是空穴的浓度，从而得到电子的迁移能为0.76 eV。在<Al_2><O_4>100- 1000 K温度范围内，用1 MeV电子辐照化学抛光的Mg样品，未发现环。另<Al_2><O_4>一方面，用6 keV的&lt;Ar^+&gt;离子辐照Mg，则显示出细小的环，其特征为1/6<111>间隙型，在1 MeV的电子辐照下不稳定。对镁合金位错环行为机制的研究<Al_2><O_4>正在进行中。

The objective of the project is to find out methods for determining migration properties of point defects in metal oxides through observations of defect aggregations during irradiation in a high voltage electron microscope. Results have been obtained on dislocation loop kinetics and migration energies of point defects in MgO, <Al_2> <O_3> and Mg <Al_2> <O_4> , and they are summerized as follows:1. The volume density <C_L> and the diameter D of loops in MgO are shown for MgO as a function of the electron flux <phi> , irradiation time t and irradiation temperature T by <C_L> <proportion> <phi^(1/2)> <t^theta> /( <M_I> ) <^(1/2)> and D <proportion> <t^(1/3)> for T<900K and by D <phi^(1/2)> <M_U> for T>900K, where <M_I> and <M_U> are respectively the mobility of interstitials and vacancies. The experimental results on <C_L> and D give the migration energies of the siower interstitial and vacancy as 0.05 eV and 2.0 eV, respectively.2. The dependence of <C_L> and D on <phi> and t for <Al_2> <O_3> containing holes is expressed by <C_L> <proportion> <phi^2> t/ <M_I> <Cu_O^2> and D <phi> t/ <Cu_O> , where <Cv_O> is the concentration of holes, yielding migration energy of interstitials as 0.76 eV.3. No loop is detected in chemically polished Mg <Al_2> <O_4> irradiated by 1 MeV electrons at 100-1000K. Mg <Al_2> <O_4> irradiated by 6 keV <Ar^+> ions, on the other hand, shows tinny loops, which are 1/6<111> interstitial type in character and are not stable under 1 MeV electron irradiation. A study on the mechanism of the dislocation loop behavior for Mg <Al_2> <O_4> is under the progress.