Patent ID: 8226922

Claim:
A high-hardness conductive diamond polycrystalline body formed substantially with diamond, wherein said diamond has a maximum particle diameter of at most 100 nm and an average particle diameter of at most 50 nm, and a particle of said diamond includes at least 100 ppm and at most 1,000 ppm of boron as a solid solution, said boron is included in a lattice site of said particle of said diamond, said high-hardness conductive diamond polycrystalline body is obtained by directly converting a graphite-type carbon material including boron as a solid solution into diamond without adding a sintering aid and catalyst, and concurrently sintering at high temperature and high pressure, so that said boron is included in a lattice site of said particle of said diamond, and B 4 C as a non-diamond phase is not included in the high-hardness conductive diamond polycrystalline body.