When comparing CVD vs HPHT diamonds, one must first understand the differences between them. Both techniques use a chemical reaction to grow diamonds, which can be either synthetic or natural. A CVD diamond is created when carbon is heated at a temperature of about 1500 degrees Celsius, or 2700 degrees Fahrenheit. A pressure of 1.5 million pounds per square inch melts this layer, and the carbon dissolves and solidifies into a diamond. After cooling, the diamond solidifies into a crystal. This process is carried out by a split-sphere press, belt press, or cubic press. The split-sphere press is the most efficient method of growing diamonds.
Differences between CVD and HPHT diamonds
The first major difference between CVD and HPHT diamonds is the process of growth. HPHT creates a temperature difference between the carbon source and the diamond growth seed, allowing the carbon atoms to diffuse through a molten flux. However, color-causing impurities were a common problem in the HPHT development process, resulting in fancy-colored diamonds. Recent advances in growth techniques have made it possible to control the impurity content very precisely.
While CVD and HPHT diamonds are identical in terms of appearance, HPHT produces diamonds with blue nuance. This is due to boron impurities, which is a common component in fancy blue diamonds. Fortunately, this color difference is not significant in diamond selection. Neither method produces more flawless diamonds than natural diamonds, so you should look for a flawless, colorless diamond. CVD and HPHT are two processes used to create diamonds. They both have the same structure and properties, but the process used to create these diamonds differs in several ways. The difference between cvd vs hpht is in the material used to create the diamond, which is usually black flux. Inclusions in natural diamonds are often dark, colored minerals such as graphite. Inclusions in HPHT diamonds are typically colorless and nitrogen-deficient.
Process of growing CVD diamonds
The process of growing CVD diamonds begins by placing a thin ‘seed’ diamond in a chamber. The chamber is filled with a carbon-rich gas mixture, usually hydrogen and methane. The gas is ionized to break molecular bonds, allowing pure carbon to attach to the diamond seed. The ionized carbon then forms atomic bonds with the diamond seed, creating a new diamond.
Unlike natural diamonds, CVD diamonds display characteristic strain patterns. These strain patterns differ slightly from natural diamonds. The diamonds can be viewed under a diamond-view machine, which uses high-energy ultraviolet radiation to reveal their inclusions. While inclusions are present in all diamonds, the CVD diamonds’ inclusions are far less prominent. These differences help distinguish synthetic diamonds from natural ones. Naturally formed diamonds also have a high degree of transparency.
The natural diamond is comprised of 99.99% carbon, but CVD diamonds contain some impurities caused by the growing process. These diamonds are characterized by silicon inclusions, which are remnants of the CVD process. Natural diamonds contain no silicon. However, a CVD diamond may look more perfect than its natural counterpart. If you’re looking for the perfect diamond, this process may be for you.
Type IIb colorless HPHT diamond
A Type IIb colorless HPHT diamond has the spectral signature of a brown-red-colored gem, and the presence of excess boron is indicative of blue nuance. This substance is usually introduced during the HPHT growth process as a nitrogen source, which is difficult and costly to remove. The presence of excess boron in a diamond is a red flag indicating that the grower took shortcuts.
The most reliable and efficient method for determining HPHT treatment in a Type IIa colorless diamond is photoluminescence spectroscopy. However, this method does not work by itself; you need to add other instrumentation. Additionally, you must have a sample of a natural type IIa diamond. This method detects the absorption of N3 at 415 nm, which is the signature of IaA or IaB-type nitrogen defects.
The HPHT synthetic diamonds are classified into four types, namely type IIa, IIb, and IaA+Ib. Type IIa diamonds are almost completely colorless and were created using HPHT. Type IIb diamonds are rarer than their counterparts, so if you want to purchase a diamond, you should look for a natural one. You should not be surprised if you find a blue HPHT diamond in your home.