CVD Vs HPHT Diamonds
When comparing diamonds, it’s important to remember that CVD diamonds are less expensive than hpht diamonds. They also have fewer impurities and brown hues, and are usually less prone to strain lines. This makes them a better option for people who want a diamond that’s as flawless as possible.
Less expensive
The CVD process is more common than HPHT, and it is cheaper because it uses smaller machinery. This method was already being used in other industries, but clever people decided to apply it to the production of diamonds. Unlike HPHT, CVD diamonds are colorless.
This method uses much less pressure and heat than HPHT to create diamonds. Carbon-based gases are introduced into a sealed chamber and heated to several hundred degrees. This breaks down the carbon atoms surrounding the diamond seed. However, the downside to CVD diamonds is that they usually come out brown or black in color. They must then undergo HPHT treatment to become colorless. However, CVD diamonds have made significant improvements over the past decade.
If the CVD diamonds are of higher quality, they can cost two or three times as much as comparable HPHT diamonds. Despite the difference in quality, a good quality CVD diamond can be sold for two to three times more expensive than a similar size and shape on a budget ecommerce site.
Has a brown hue
Diamonds with a brown hue are a common trait of CVD synthetic diamonds, despite their labelling as “synthetic.” These diamonds are extremely similar to naturally-grown diamonds, and only an experienced jeweler would be able to tell the difference. In fact, the Federal Trade Commission ruled in 2018 that synthetic and natural diamonds are identical.
The CVD process creates diamonds from tiny crystals. It begins by breaking down a gas of carbon and depositing it onto the seed crystal. As the carbon deposits, it builds up to form a diamond. Unlike HPHT diamonds, CVD diamonds grow in thin layers, and their size is determined by the amount of time the process takes. Additionally, these diamonds don’t require high temperatures or high heat.
In addition, the HPHT diamonds are more expensive than their CVD counterparts, and they often have a brown tint. However, a CVD diamond won’t contain metal inclusions, unlike a diamond made using HPHT. However, a brown hue is possible with CVD diamonds when the process is done too quickly. However, the brown colour can be removed by changing the gas in the chamber. For example, you could replace the gas with nitrogen or boron to create a yellow or blue diamond.
Has no strain lines
In natural diamonds, the strain lines present in the crystal lattice are caused by the heavy pressure applied during the formation process. These lines give natural diamonds their characteristic mosaic-shaped or criss-cross pattern. In contrast, HTHP diamonds are created under the same conditions as natural diamonds, but with controlled pressure and temperature. Because of this, there are no strain lines present in HTHP diamonds. However, unlike HTHP diamonds, CVD diamonds experience fluctuating pressure and temperature, causing them to display strain lines.
Natural diamonds have a sharp peak of luminescence at 300 nm, which indicates their natural origin. However, CVD diamonds exhibit characteristic peaks at 3123, 3659, and 3600 cm-1, which are the first vibrational replicas of NV-center. Thus, the luminescence of CVD diamonds is not related to their color, and is therefore useful in identifying them.
Has minimal to no impurities
CVD vs HPHT diamonds are very similar in appearance, but they have slightly different properties. HPHT diamonds are more transparent and do not have strain lines, while CVD diamonds often do. HPHT diamonds are blue in color due to the presence of boron impurities.
Infrared absorption occurs in two or three phonon processes, and is temperature dependent. Molecular structures of diamonds are determined using Raman spectroscopy, which can detect defects in the diamond’s structure. Spectral analysis of the diamond’s surface reveals that its properties are strongly affected by impurity content and grain structure. A finer grained diamond has a higher thermal conductivity and better mechanical properties.
A CVD diamond is classified as having minimal to no impurities, while an HPHT diamond may contain impurities. The difference between a natural diamond and a CVD diamond comes down to the manufacturing process. HPHT diamonds tend to contain impurities in excess levels due to metal influx during the diamond making process. This can negatively affect the diamond’s physical and chemical properties.
Has no cracks or breaks during treatment
The chemical vapor deposition process involves the use of high-pressure, high-temperature chemicals to create a diamond. To form a high-quality diamond, the CVD process starts with the strongest natural diamond. This seed is then placed in a chamber with high-carbon gas concentrations. These gases are then exposed to high temperatures and pressures, which transforms them into a plasma, which helps build the diamond layers.
Conclusion
While this treatment improves the color of the diamond, it does not alter the clarity grade. Inclusions and cracks are filled with glass-like material, which gives the diamond its color and transparency. Consequently, a crack or break will appear invisible. However, the diamond will not be as transparent as a natural diamond, and it may still be visible under certain light sources.
