Synthesis and characterization of strip-shape diamonds from Fe-based alloy and graphite system under high pressure and high temperature

The unusual strip-shape diamond crystals were successfully synthesized in the system of Fe-based powder alloy and graphite under pressures of 5.6–5.8 GPa and temperatures of 1600–1650 K in a cubic anvil high pressure high temperature (HPHT) apparatus (SPD-6×1200). The synthetic diamond crystals have a strip-shape with light green color. The lengths of the crystals are 0.6–0.8 mm with length to diameter ratios around 2.0–2.5. SEM photographs reveal that the crystals have two main kinds of shapes: one elongated along the (1 0 0) and the other along the (1 1 1) directions. The FTIR spectra of the diamond synthesized indicate that its nitrogen concentration is higher than the normal diamond crystal.