Crystal Growth and Characterization of Diamond from Carbonyl Iron Catalyst under High Pressure and High Temperature Conditions

We have explored diamond synthesis from carbonyl iron powder catalyst to investigate the effects of minor elements on diamond crystallization in a series of experiments at temperatures of 1200–1800 °C and pressures of 5.0–7.0 GPa. Our results show that the diamond morphology is not only determined by pressure and temperature conditions but is also significantly influenced by the composition of crystallization medium. The stable growth forms of diamond are strip and lamellar shapes at relatively low temperature conditions. We have established the essential dependence of diamond morphology and nucleation peculiarities on the composition of crystallization medium and P/T conditions in the P–T diagram. Furthermore, we find two different diamond growth modes existing in the studied systems. The current study suggests that the novel growth habits of the diamond could be attributed to the common effect of nitrogen and oxygen elements on the diamond crystallization.