Effects of additive LiF on the synthesis of cBN in the system of Li3N-hBN at HPHT

High-quality cBN single crystals were successfully synthesized in the system of Li3N-hBN with additive LiF at high pressure and high temperature (HPHT). The lowest synthetic conditions of cBN decreased to 4.6 GPa, 1320 C by employing 3 wt.% LiF, and it didn't change anymore though more than 3 wt.% LiF had been added. The quality of cBN crystals improved markedly. The cBN crystals and other products were examined by X-Ray diffraction and scanning electron microscopy. The X-Ray analysis reveals that the "graphitization index" (GI) of hBN increased by adding 3 wt.% LiF into the system of Li3N-hBN at HPHT. The SEM photographs show that different growth steps were formed on the cBN crystal surface in systems of Li3N-hBN and Li3N-LiF-hBN, respectively. (C) 2010 Elsevier B.V. All rights reserved.