Inclusions in large diamond single crystals at different temperatures of synthesis

The inclusions in large diamond single crystals have effects on its ultimate performance, which restricts its industrial applications to a great extent. Therefore, it is necessary to study the inclusions systematically. In this paper, large diamond single crystals with different content values of inclusions are synthesized along the (100) surface by the temperature gradient method (TGM) under 5.6 GPa at different temperatures. With the synthetic temperature changing from 1200 degrees C to 1270 degrees C, the shapes of diamonds change from plate to low tower, to high tower, even to steeple. From the microscopic photographs of the diamond samples, it can be observed that with the shapes of the samples changing at different temperatures, the content values of inclusions in diamonds become zero, a little, much and most, correspondingly. Consequently, with the temperature growing from low to high, the content values of inclusions in crystals increase. The origin of inclusions is explained by the difference in growth rate between diamond crystal and its surface. The content values of inclusions in diamond samples are quantitatively calculated by testing the densities of diamond samples. And the composition and inclusion content are analyzed by energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). From contrasting scanning electron microscopy (SEM) photographs, it can be found that the more the inclusions in diamond, the more imperfect the diamond surface is.