Synthetic Sapphire Crystal

Single Crystal Aluminum Oxide

Saint-Gobain Crystals’ industrial single crystal sapphire is highly pure, with minimal contamination, no grain boundaries, and minimal defects; giving it a range of desirable properties.

  • It's hard and almost impossible to scratch.
  • It’s chemically inert.
  • It transmits light without interference.
  • It conducts heat but is an electrical insulator.
  • It is temperature resistant.

With over 50 years of experience, our capabilities in the growth, processing and production of industrial sapphire ensure consistent highest quality and excellent transmission.

Industrial Sapphire's unique properties make it a cost-effective solution where high performance and long life are critical, including extreme physical conditions such as high-temperature, high-pressure or harsh chemicals.

One of the hardest materials in existence, sapphire is virtually scratch-proof which helps it maintain its integrity in demanding physical environments. It has a melting point of over 2000°C, making it ideal for high-temperature applications. It is chemically inert and easily withstands harsh chemicals such as fluorine plasma and other industrial gasses and fluids, with no particle generation and due to its purity and transparency, it can be used as a viewing window in high pressure and vacuum applications. In addition, sapphire can transmit ultraviolet, visible and infrared light as well as microwaves, a range broader than most materials.

Saint-Gobain’s sapphire growth and production finishing capabilities have been designed and developed to deliver the broadest range of sapphire products from a single source.

Edge Fed Growth technology enables the production of large, continuous single crystal sapphire pieces to produce tubes (up to 3” diameter) and windows (1 ft x 3 ft). With this growth technology, the shape and size of a sapphire crystal to controlled during its formation.

Pushing the boundaries, the team recently produced the world’s largest single crystal Sapphire tube at 2.5” outer diameter x 30” Long and developed the process to curve Sapphire sheets.

Explore our industrial sapphire crystals in a range of shapes; flat and curved sheets, tubes, pins, rods and complex bonded.

Material Comparison to Saint-Gobain Single Crystal Sapphire

Material Type Density g/cc Areal Density psf/in Young's Modulus
Knoop Hardness
Fracture Toughness
Thermal Conductivity
Thermal Expansion
SAPPHIRE Ceramic 3.9 20.2 435 2000 2 32 60
ALON® 3.69 19.2 323 1850 2 9.6 56
Spinell 3.58 18.6 277 1645 1.5 - 2 14.7 60
Soda-Lime Glass Glass 2.52 13.1 69.6 585 0.75 0.9 - 1.3 90
Li-Alumino-Silicate Glass-Ceramic 2.52 13.1 88.5 570 1.1 1.6 - 1.3 0


Sapphire Properties

  • Single (Al2O3) crystal, highest purity possible, no grain boundaries
  • Minimal to no particle contamination
  • High melting point, 2053oC
  • Hardness next to diamond on Mohs Scale of Hardness: extremely scratch-resistant
  • Chemically inert (non-reactive in most process environments)
  • Superior rigidity (435 Gpa, 6x stiffer than quartz)
  • Transparent - transmits UV - visible - IR wavelengths
  • Radiolucent
  • Can be made in complex shapes
Properties Value
Density  3.97 gm/cm3 (0.143 lb/in3) (25°C)
Young’s Modulus 435 GPa (63 x 106 psi) parallel to C-axis (25°C)
386 GPa (56 x 106 psi) parallel to C-axis (1000°C)
Modulus of Rigidity (Shear Modulus) 175 GPa (26 x 106 psi)
Flexural Strength 1035 MPa (150 kpsi) parallel to C-axis (25°)
760 MPa (110 kpsi) perpendicular to C-axis (25°)
Compressive Strength ≈2 GPa (300 kpsi) (25°)

9 on Mohs scale (between 20° and 25°C)

1900 Knoop parallel to C-axis
2200 Knoop perpendicular to C-axis

Properties Value
Transmission UV through midwave IR (~200-5000nm)
Uniaxial Negative Refractive Index Ordinary ray (C-axis) No = 1.768
Extraordinary ray Ne-1.760
Birefringence: 0.008
Temperature Coefficient of Refractive Index 13 X 10-6/°C (visible range)
Spectral Emittance 0.1 (1600°C)
Spectral Absorption 0.1 – 0.2cm-1 (0.66 μm, 1600°C)
Properties Value
Melting Point 2053°C (3727°F)
Specific Heat 0.181 cal/gm°K (25°C)
0.300 cal/gm°K (1000°C)
Thermal Conductivity 0.4 watts/cm°K (25°C)
0.1 watts/cm°K (1000°C)
Thermal Expansion Coefficient (25 – 1000°C)
8.8 x 10-6; parallel to C-axis
7.9 x 10-6; perpendicular to C-axis
Size Range

Standard available sheet product features include:

  • Unpolished, “As Grown”, thickness from .060” to .500” (1.5 to 12.7 mm)
  • Polished thickness from .030” to .35” (0.76 to 8.9 mm)
  • Widths to 12.0” (304 mm), Lengths to 81.0” (2057 mm)
  • Disk diameters 0.125” to 12.0” (3.1 to 304 mm)

Standard available tube sizes range from .06” to 1.7” (1.5 mm to 43.0 mm) outside diameter
Standard available rod sizes up to .30” (7.6 mm) diameter and 40.0” (1016 mm) length


Sapphire (Al2O3) Material Properties Brochure

PDF | 1.21 MB

In this article, we outline the properties of sapphire and take a look at how Edge-Fed-Growth is enabling the production of large and complex sapphire

PDF | 532.89 KB