Nanosized crystalline foreign particles contained in cubic boron nitride single crystals

Cubic boron nitride (c-BN) crystals with a dimension of 0.3–0.4 mm, which have been synthesized using lithium nitride (Li3N) as a catalyst under high temperature–high pressure (HPHT), were examined by transmission electron microscopy (TEM). It was shown by TEM that there exits some nanostructrued areas containing several types of nanosized foreign particles within the as-grown c-BN crystals. The results indicate that the nanometer inclusions are hexagonal BN (h-BN) with a lattice constant of a=2.054 Å, c=6.661 Å, tetragonal B25N with a lattice constant of a=8.79 Å, c=5.08 Å, tetragonal B53N with a lattice constant of a=8.79 Å, c=5.08 Å, and hexagonal Li3N with a lattice constant of a=3.648 Å, c=3.875 Å.