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Kyropoulos 
Sapphire

What is Kyropoulos Sapphire

Kyropoulos Sapphire refers to synthetic Sapphire crystals produced using the Kyropoulos method, a technique primarily used to grow large, high-quality single crystals of Sapphire (Al₂O₃). This method is different from the Verneuil process and is more suited to applications requiring larger and purer crystals, such as in optics and electronics.

Technical informations

Growth Process
The crystal grows in a large crucible so large boules are possible
Slow cooling to minimize stress and defects
Material growth starts from a seed crystal precisely placed in the crucible to define material orientation
Chemical Composition
Minimum 99.99% Al2O3 (Aluminum oxide)
Kyropoulos Sapphire is chemically identical to natural Sapphire, consisting of pure aluminum oxide with minimal impurities
Physical Properties
Hardness 9 on the Mohs scale, only second to diamond
Density Approximately 3.98 g/cm³
Transparency High transparency, often with fewer internal flaws or inclusions than Sapphires grown with Verneuil method
Optical Properties
Clarity High clarity with fewer inclusions
Refractive Index 1.762 - 1.770
Birefringence 0.008 – 0.011
Transmission range 0.15 to 5.5 micron (from UV to mid-IR)
Mechanical Properties
Strength High mechanical strength, making it suitable for high loads
Wear Resistance Exceptional wear resistance due to its hardness
Thermal Properties
Melting Point Around 2,050°C, like all corundum-based materials
Thermal Conductivity 25 W/mK at 300K
Thermal Shock Resistance Excellent. Good for applications with rapid temperature changes
Market Value
Lower internal stress and fewer defects means easier cutting, polishing and shaping into wafers, domes and lenses
Ideal for infrared (IR) windows

Kyropoulos Sapphire applications

Due to the method of growth, Kyropoulos Sapphires are often used in high-precision optical applications.

Optics and Electronics

Kyropoulos Sapphires are widely used in high-tech industries, including for LED
substrates, optical windows, watch faces, and in scientific instruments.

Aerospace

Used in windows for spacecraft due to its high clarity, strength, and thermal resistance.

Jewelry

Although it is primarily used for industrial purposes, high-quality Kyropoulos Sapphire can be cut into gemstones for jewelry.

Download technical sheet

The Kyropoulos method: how it works

The Kyropoulos method is a crystal growth technique invented in the 1920s by Spyro Kyropoulos. The process begins with a crucible filled with molten alumina (Al₂O₃) at very high temperature. A small seed crystal is dipped into the melt and slowly pulled upwards while the temperature is carefully lowered.

Unlike other methods, the seed remains in contact with the melt during most of the process. This allows the crystal to gradually expand in diameter, growing into a large, stress-free sapphire boule. The slow cooling and controlled growth environment ensure excellent transparency and mechanical properties, making the resulting sapphire suitable for both industrial and scientific applications.

FAQ

What is Kyropoulos Sapphire? The Kyropoulos method is a technique primarily used to grow large, high-quality single crystals of Sapphire.
How is Kyropoulos Sapphire produced? Kyropoulos Sapphire is produced by melting high-purity alumina in a crucible at very high temperature. A small seed crystal is then dipped into the melt and slowly cooled under precise control. Instead of pulling the crystal quickly, as in other methods, the Kyropoulos process allows it to grow gradually in diameter while remaining in contact with the melt. This slow, controlled cooling creates large, high-quality sapphire boules with excellent clarity and minimal internal stress.
Can you manufacture custom geometries or micro-components? Yes, we produce both standard and fully customized Sapphire components, including complex shapes and micro-parts with tight tolerances, tailored to your specifications.
Do you provide prototypes? Yes, we support the development of prototypes and pre-series batches, allowing you to test performance and functionality before moving into full-scale production.
Is there a minimum order quantity? No, we handle both single custom parts and large production runs. Our process is designed to meet your volume requirements without compromising on quality or precision.
Do you ship internationally? Yes, we serve clients worldwide and manage international logistics, ensuring smooth delivery regardless of your location.

Want more information about our Kyropoulos Sapphire? We can also design a custom solution tailored to your application.

We are proud of our products and different material properties. We will be happy to answer your technical and detailed questions about our Kyropoulos Sapphire

*The technical specifications and material information provided on this website adhere to industry standards and are not determined by our company. While we strive to ensure accuracy, these details are for informational purposes only and may be subject to change.