Pathways to c-BN from melts at atmospheric pressure

Abstract The industrial synthesis of cubic boron nitride is performed under high pressure and high temperature from the hexagonal phase with catalysts. Since it has been demonstrated that c-BN is the stable BN modification under standard conditions, there should also be a way to synthesize the superhard c-BN phase at normal or low pressure. To reach this goal growth conditions with high mobility for both the B and the N species have to be found. Melts containing Li/B/N could be a possible solvent to form c-BN analogous to the high-pressure synthesis, whereby Li 3 BN 2 is acting as a solvent-catalyst. Under normal pressure possible interactions of two different c-BN samples with various phases from the ternary Li-B-N phase system were investigated at temperatures up to 950 °C. The following melts were applied: elemental lithium (Li), lithium fluoride (LiF), lithium nitride (Li 3 N), lithium boride (Li 7 B 6 ), lithium boronitride (Li 3 BN 2 ) and boronoxide (B 2 O 3 ). After these melt treatments morphological and other changes of the c-BN crystals were examined by SEM, Raman spectroscopy and XRD.