Formation and crystal structure of metallic inclusions in a HPHT as-grown diamond single crystal

One of the most important characteristics associated with crystal growth te chnology is the entrapment of inclusions by the growing crystal. Diamond si ngle crystals prepared under high temperature-high pressure (HPHT) usually contain metallic inclusions. In the present paper, metallic inclusions in a diamond grown from a Fe-Ni-C system using the HPHT method have been, for t he first time systematically examined by transmission electron microscopy ( TEM). Energy dispersive X-ray spectrometry (EDS), combined with selected ar ea electron diffraction (SAD) patterns, has been used to identify the chemi cal composition and crystal structure of the metallic inclusions. The metal lic inclusions were found to be composed mainly of cubic gamma-(FeNi), face -centered cubic (FeNi)(23)C-6, ortho-rhombic Fe3C and hexagonal Ni3C, which may have been formed through the entrapment of molten catalyst by the grow th front or through reaction of the trapped melt with contaminants in the d iamond.