Russian scientists developed superconducting diamonds
Diamond is originally an electrical insulator with extremely high hardness and thermal conductivity better than copper. These excellent properties are due to its special structure and covalent bonds. If other elements are incorporated into the diamond as carriers, it becomes an electrical conductor. A boron atom has one electron less than a carbon atom, and can generate an effective hole in the diamond to become a charge acceptor. The acceptor level generated by the hole introduced by the boron atom is located at the top of the valence band of the diamond, and the distance from the conduction band is about 5.5. Electronic volts. Compared with other potential doping elements, boron has a small atomic radius, is easy to enter the diamond lattice, and is easy to obtain a higher doping concentration. Electron conduction studies of boron-doped diamonds have shown that when the boron atom concentration is n ≈ 1017 to 1019 / cm 3 , an activation energy of about 0.35 electron volts is generated. As the boron concentration increases, the activation energy will gradually decrease. When n≥1020/cm3, the boron-doped diamond exhibits metalloid behavior, and the value 1020 is called the insulator-metal transition concentration.
Scientists reacted B4C and graphite at high temperature (2500 ~ 2800K) and high pressure (about 1010Pa) to obtain polycrystalline clusters with a metal-like luster diameter of 1-2 mm. The diameter of the boron-doped diamond grains was only a few. Micron, and physical properties such as resistivity, magnetic permeability, specific heat, etc. indicate that boron-doped diamond belongs to type II superconductor and exhibits superconducting properties below the superconducting transition temperature Tc ≈ 4K. The discovery of the superconducting properties of carbon in diamond-type structures suggests that scientists, silicon and germanium with the same structure may also produce superconductivity under suitable conditions.