Laboratory grown diamond is also called, Synthetic diamond, labgrown diamond, cultured diamond or cultivated diamond.
Laboratory grown diamond is a diamond made in the laboratory by man. It has the same physical and chemical characteristics as a natural diamond composition, hardness, brilliance, luster, etc. Therefore, it is not a fake diamond but a diamond that is not natural.
A brief history
It was in 1954 when General Electric More specifically Tracy Hall published his research and results in Nature magazine. It was then that the creation of the first labgrown diamond was officially recognized.
The first real use of labgrown diamonds in jewelry (gem quality) began in the mid-1990s. But it was not until the late 2010s that these synthetic stones began to gain ground in jewelry.
Diamonds, when they reach a certain degree of purity, have exceptional mechanical, optical, thermal and electronic properties. Labgrown diamonds can be artificially “treated” with boron, phosphorous or nitrogen. The introduction of defects in the crystal structure (for example, the formation of a new crystal) can be used to modify the electronic properties of the material. The introduction of defects in the crystal structure (nitrogen-lacuna centers or NVs, for example) is also used in quantum physics.
A diamond can be monocrystalline or polycrystalline, that is, made up of many smaller crystals. Large, clear, single crystal diamonds are often used in jewelry.
Synthetic diamond is the hardest known material. Hardness is defined as resistance to scratching and is rated from 1 (softest) to 10 (hardest) on the Mohs scale of mineral hardness.
The hardness of a synthetic diamond depends on its purity, the perfection of the crystal and its orientation: the hardness is higher for pure and flawless crystals.
impurities and inclusions
Each diamond contains atoms other than carbon in concentrations detectable by analytical methods. These atoms can be grouped into macroscopic phases called inclusions. Impurities are generally avoided, but may be incorporated, as a means of controlling certain properties of the diamond.
For example, a pure diamond is an electrical insulator, but a diamond with added boron is a conductor, and in some cases a superconductor.
The HPHT (High Pressure, High Temperature) technique consists of mixing carbon (in abundant form) and transition metals (which will act as catalysts) and subjecting the whole to very high pressure (about 58,000 atmospheres) and temperature (about 1400 °C). The diamond is then formed by germination and growth. In the temperature gradient method, a diamond seed is introduced into the reactor prior to reaction.
The CVD technique (Chemical Vapor Deposition; in French Chemical Vapor Deposition) consists of growing the diamond in successive layers. The method consists of placing a layer of diamond (substrate or seed) in a chamber with a pressure of one tenth of an atmosphere. From hydrogen and methane (precursor gases) and the whole is ionized with a microwave (frequency 2.45 GHz). A plasma and the resulting species (ions, radicals, etc. from the initially injected gases) are adsorbed on the substrate. The formation of a diamond layer that grows with time takes place after diffusion and surface reaction of the reactive species.
Difference with natural diamonds
Differentiating between synthetic and natural diamonds is difficult and may require special equipment.
Natural diamond giant De Beers is developing several techniques to detect these new diamonds. One of these techniques is to detect the growth form of the diamond, which is not the same as in nature. For example, diamonds obtained by the HPHT method create cube-shaped growth sectors. Some forms of impurities are also not found in nature.
The CVD method, on the other hand, produces diamonds that are more difficult to differentiate from natural ones, since they are very pure and the impurities and cubic growth zones are less distinguishable.
A synthetic diamond is evaluated according to four criteria, exactly the same as a natural diamond: the 4 Cs: Carat (the weight of the diamond), Color (the color of the diamond), Clarity (the purity of the diamond), and Cut (the size of the diamond). ).
The main gemological laboratories that issue certificates for natural diamonds also issue certificates for synthetic diamonds, using exactly the same criteria to define their characteristics. The only difference between the two certificates is that one says “Natural Diamond” and the other “Laboratory Grown Diamond.”