Synthesis of Cubic Boron Nitride by the Reaction of Li3N and B2O3

  • Cubic boron nitride is synthesized by the reaction of Li3N and B2O3 under high pressure and high temperature (4.0--5.0GPa, 1350--1500°C). The minimum pressure of cBN formation is 4.0GPa. The present condition of cBN formation is clearly lower than the eutectic temperature of Li3BN2 and BN in the Li3N-hBN system (5.5GPa, 1610°C). The content of cBN in the sample increases, while the content of hBN decreases with the temperature and pressure. The maximum conversion rate (5.0GPa, 1500°C) is about 34%, which is higher than that in the hBN-Li3N system. The cBN crystals are octahedral or tetrahedral in shape and approximately 20μm in diameter.
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