CVD (Chemical Vapor Deposition) diamonds exhibit fluorescence, a phenomenon where the diamond emits visible light when exposed to ultraviolet (UV) radiation. This fluorescence is influenced by the presence of impurities and defects in the diamond's crystal structure, which are introduced during the CVD growth process. The fluorescence colors observed in CVD diamonds can range from green, yellow-green, yellow, orange, to red. This property is not only a distinguishing feature but also a useful tool for identifying CVD diamonds, as the fluorescence patterns and colors can differ from those of natural diamonds.
Key Points Explained:
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Fluorescence in CVD Diamonds:
- Fluorescence is the emission of visible light when a material is exposed to UV light. In CVD diamonds, this is primarily caused by the presence of nitrogen-vacancy (NV) centers and other defects in the crystal lattice.
- The fluorescence colors in CVD diamonds can vary widely, including green, yellow-green, yellow, orange, and red. This variation is due to the different types and concentrations of defects and impurities present during the diamond's growth.
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Optical Properties of CVD Diamonds:
- CVD diamonds have excellent optical properties, including high transmittance from deep ultraviolet (0.23 μm) to microwave wavelengths. This broad range of transmittance makes them suitable for various optical applications.
- The refractive index of CVD diamonds is 2.376 at a wavelength of 10 μm, which is similar to that of natural diamonds, contributing to their brilliance and sparkle.
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Inclusions and Clarity:
- The clarity of CVD diamonds is influenced by the atmosphere in which they are grown. Inclusions, which are internal features or defects, can affect both the clarity and texture of the diamond.
- Some inclusions are visible to the naked eye, while others are microscopic. High temperatures during the CVD process can increase the presence of these inclusions, affecting the diamond's overall clarity.
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Surface and Grain Structure:
- The surface roughness of CVD diamonds evolves with thickness, and the grain structure is non-uniform due to the growth process. This can affect the diamond's optical properties and fluorescence.
- The non-uniform grain structure can also lead to variations in fluorescence intensity and color across different parts of the diamond.
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Applications and Benefits:
- CVD diamonds are known for their increased hardness and wear resistance compared to PCD (Polycrystalline Diamond). They are particularly effective for machining materials like long-chipping aluminum and magnesium alloys, high-silicon aluminum, and tungsten carbide.
- The unique fluorescence properties of CVD diamonds can be used in various applications, including gemological identification and optical devices.
In summary, the fluorescence of CVD diamonds is a complex phenomenon influenced by the diamond's crystal structure, impurities, and growth conditions. Understanding these factors is crucial for both gemological identification and the effective use of CVD diamonds in industrial applications.
Summary Table:
| Aspect | Details |
|---|---|
| Fluorescence Colors | Green, yellow-green, yellow, orange, red |
| Causes | Nitrogen-vacancy centers, defects, and impurities in the crystal structure |
| Optical Properties | High transmittance (0.23 μm to microwave), refractive index of 2.376 at 10 μm |
| Inclusions & Clarity | Affected by growth atmosphere; inclusions vary in size and visibility |
| Applications | Gemological identification, optical devices, machining hard materials |
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