Shibata N, Chisholm M F, Nakamura A, Pennycook S J, Yamamoto T, Ikuhara Y
Institute of Engineering Innovation, University of Tokyo, 2-11-16, Yayoi, Bunkyo, Tokyo 113-8656, Japan.
Science. 2007 Apr 6;316(5821):82-5. doi: 10.1126/science.1136155.
Little is known about dislocation core structures in oxides, despite their central importance in controlling electrical, optical, and mechanical properties. It has often been assumed, on the basis of charge considerations, that a nonstoichiometric core structure could not exist. We report atomic-resolution images that directly resolve the cation and anion sublattices in alumina (alpha-Al2O3). A dissociated basal edge dislocation is seen to consist of two cores; an aluminum column terminates one partial, and an oxygen column terminates the second partial. Each partial core is locally nonstoichiometric due to the excess of aluminum or oxygen at the core. The implication for mechanical properties is that the mobile high-temperature dislocation core structure consists of two closely spaced partial dislocations. For basal slip to occur, synchronized motion of the partials on adjacent planes is required.
尽管位错核心结构在控制氧化物的电学、光学和力学性能方面至关重要，但目前人们对其了解甚少。基于电荷考虑，人们常常认为非化学计量比的核心结构不可能存在。我们报告了原子分辨率图像，这些图像直接分辨出了氧化铝（α-Al₂O₃）中的阳离子和阴离子亚晶格。观察到一个解离的基面边缘位错由两个核心组成；一个铝柱终止一个分位错，一个氧柱终止第二个分位错。由于核心处铝或氧的过量，每个分位错核心在局部是非化学计量比的。这对力学性能的影响是，高温下可移动的位错核心结构由两个紧密间隔的分位错组成。为了发生基面滑移，相邻平面上的分位错需要同步运动。
