Synthesis of cubic boron nitride using magnesium as the catalyst

Cubic boron nitride (CBN) single crystals have been synthesized employing the BN-Mg system under high pressure and high temperature conditions. During the exploration of the thermodynamically stable CBN growth region it has been found that apart from the CBN phase the other crystalline phases formed during the chemical reaction are: MgO, Mg 3(BO 3) 2, Mg 3N 2, MgB 6, or MgB 12. Along with these catalytic phases the wurtzitic boron nitride (WBN) has also been detected and reported for the first time. The role of various phases formed during the reaction has been examined and a possible explanation for the formation of WBN has been suggested. The morphology of CBN crystals and their yield have been studied as a function of temperature and pressure. The effect of oxygen impurity present in the starting hexagonal boron nitride (HBN) on the conversion to CBN has also been discussed.