CVD Vs HPHT Diamond

A CVD diamond is a diamond that has a low through-plane conductivity and a low birefringence. While this is an excellent property for a diamond used in jewelry, it does have some drawbacks as well. These include a slightly higher price tag and a lower color grade than an HPHT diamond.

Low birefringence single crystal CVD diamond

The low birefringence single crystal CVD is characterized by low stress and low birefringence. This characteristic allows this material to exhibit low wear rates and be suitable for applications where birefringence is not a limiting factor. These characteristics make it ideal for water jet nozzles, stichels, and analysis windows.

The single crystal CVD diamond material should have a total nitrogen concentration of 3 ppm and low optical birefringence. In addition, the diamond material should have an area of 1.3 mm x 1.3 mm. This material should also be chemically stable, resistant to acids and alkalis, and have a high degree of crystalline quality.

Low birefringence single crystal CVDS diamonds must be produced by a technique that can eliminate dislocations. Optical birefringence can be measured to within +/ 10 degrees, depending on the material and process. The birefringence direction is typically correlated with the direction of growth. This is because dislocations tend to propagate through materials in the growth direction.

Low through-plane conductivity

The low through-plane conductivity of diamond is largely due to the thermal phonons present in the material. Phonons are the directional wave motions of lattice ions. These are most common in dielectrics, like diamond. However, at low temperatures, these phonons are limited due to boundary scattering and impurities. This limits the thermal conduction of diamond at low temperatures.

In the study of the through-plane conductivity of diamond, two different types of diamonds were studied. The first was deposited on a p-type SiC substrate, while the second type was deposited on an n-type SiC substrate. These diamond films were deposited at low surface deposition temperatures. Microwave plasmas were used to control and monitor the temperature of the diamond film during the growth process. The growth rate of the diamond films was 1.3 mm/h on SiC substrates at a surface temperature of 530 degC. Then, the in-plane thermal conductivity was measured by the traveling wave method.

In the study of a two-mm-thick diamond film deposited on a Si3N4 substrate, the TC of this material was measured to be 638 +-48 W/mK. This is among the highest TC values reported for diamond on GaN (12,13). It is also close to the theoretical value for diamond with the same grain size. The high through-plane thermal conductivity of diamond has many applications, including thermal management.

Color grade

Color grade refers to the diamond’s overall color. Diamonds with a color grade below H are considered to be less desirable. Usually, this means that a diamond has some inclusions, which are not diamonds. Inclusions in a HPHT diamond are generally non-diamond material, such as metallic flux. HPHT diamonds also tend to have lower clarity grades than mined diamonds.

HPHT synthetics are classified as type IIb. They may be contaminated with boron during growth, or intentionally doped. In contrast, colorless diamonds are generally type IIa. HPHT diamonds that have been post-growth-treated are classified as type IIa or IIb, depending on their nitrogen concentrations.

In addition to being brown in color, cvd diamonds can show strain lines. The brown hue is caused by the fact that the diamond is grown layer by layer, and it can be minimized by increasing the color grade.


When it comes to diamonds, both Cvd Vs Hpht Diamond are incredibly beautiful. In addition to their cubic shapes, these diamonds are remarkably similar to earth-grown diamonds in terms of their optical, chemical, and physical properties. Nevertheless, the two methods are not identical and cannot be distinguished without a professional’s help.

The CVD method relies on carbon-based gases to grow diamonds. It begins with a diamond seed, usually a thin slice of diamond. However, sometimes a diamond created through the HPHT method is used as the seed for this process. Unlike HPHT, the CVD method requires a lower amount of energy.


While both methods produce high-quality diamonds, the CVD process is less costly. The HPHT process is more expensive, and requires larger equipment and higher energy.

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