Ⅰa型褐色金刚石结构缺陷的同步辐射白光形貌特征

Structure Defects in Type Ⅰa Brown Diamonds by Polychromatic Synchrotron Radiation Topography

同步辐射白光形貌术具有射线强度大、准直性好、摄谱时间短、分辨率高等特点,是无损研究晶体缺陷的有效工具.采 用该方法对产自山东蒙阴、辽宁瓦房店和湖南沅江3个矿区的31颗典型金刚石样品进行了研究.白光形貌像揭示,金刚石 中普遍存在晶体结构畸变的特征,并且变形程度不等,部分严重变形晶体具有异常劳埃衍射式样;其衍射斑点的形态、衬度 及条纹变化反映了金刚石晶体结构变形的程度和复杂性.晶格的完整性与金刚石的褐色强度无明显相关性.该类结构缺陷 与金刚石的复杂形成过程和深部保存条件有关.

Polychromatic synchrotron radiation (SR) is an effective method for the non-destructive study of diamond crystal defects. Its advantages include the use of intense X-ray, short exposure time, high collimation and high resolution. The SR method was applied to 31 diamond crystals from three major Chinese diamond mine areas:Mengyin in Shandong Province, Wafangdian in Liaoning Province and Yuanjiang area in Hunan Province. The diamond crystals generally showed structure deformation and had different degrees of deformation. Some diamonds with serious deformation demonstrated strong asterism and spot fragmentation in Laue pattern. Factors such as shape, contrast and the interior structure of reflexes in Laue patterns indicate the degree and complexity of crystal deformation. Results show that the crystal imperfections have not obvious relationship to the intensity of the diamonds' brown color. It is likely that crystal defects correlate with the complex crystallization processes and deep environment of diamonds.