Is Diamond a Conductor?

There are two types of conductivity. Thermal conductivity is a measure of how well a material conducts heat. Electrical conductivity expresses how well a substance conducts electricity. A diamond has characteristic thermal and electrical conductivity that can be used to help distinguish it from other materials and identify impurities in a genuine diamond.

Unique Mineral Qualities

Most diamonds are extremely efficient thermal conductors, but electrical insulators. Diamond conducts heat well as a result of the strong covalent bonds between carbon atoms in a diamond crystal. The thermal conductivity of natural diamond is around 22 W/(cm·K), which makes the diamond five times better at conducting heat than copper. The high thermal conductivity may be used to distinguish diamond from cubic zirconia and glass. Moissanite, a crystalline form of silicon carbide that resembles diamond, has a comparable thermal conductivity. Modern thermal probes can differentiate between diamond and moissanite, as moissanite has gained popularity.

The electrical resistivity of most diamonds is on the order of 10¹¹ to 10¹⁸ Ω·m. The exception is natural blue diamond, which gets its color from boron impurities that also make it a semiconductor. Synthetic diamonds doped with boron also are p-type semiconductors. Boron-doped diamond may become a superconductor when cooled below 4 K. However, certain natural blue-grey diamonds that contain hydrogen are not semiconductors.

Phosphorus-doped diamonds films, produced by chemical vapor deposition, are n-type semiconductors. Alternating boron-doped and phosphorus-doped layers produce p-n junctions and may be used to produce ultraviolet emitting light emitting diodes (LEDs).