Synthesis of superhard cubic BC2N

Cubic BC2N was synthesized from graphite-like BC2N at pressures above 18 GPa and temperatures higher than 2200 K. The lattice parameter of c-BC2N at ambient conditions is 3.642(2) Angstrom, which is larger by 1.48% than would be expected based on ideal mixing between diamond and cubic boron nitride. The bulk modulus of c-BC2N is 282 GPa which is one of the highest bulk moduli known for any solid, and is exceeded only by the bulk moduli of diamond and c-BN. The hardness of c-BC2N is higher than that of c-BN single crystals which indicates that the synthesized phase is only slightly less hard than diamond. (C) 2001 American Institute of Physics.