Sapphire -General Info

Sapphire glass has mechanical and thermal properties similar to technical ceramics.

Sapphire single crystal is characterized by high mechanical, chemical and thermal resistance and also offer a good optical transmission at 200 nm.

Wherever extreme demands on wear resistance, hardness, inertness, thermal and chemical resistance, sapphire is the right solution.

Specific characteristics of sapphire:

  • acid-insoluble e.g. to hydrofluoric acid, fluorine or aggressive gases
  • excellent optical transmission – from UV to IR
  • temperature resistant to 2000 ° C
  • Corrosion and abrasion resistance
  • extreme hardness, high strength (Mohs hardness 9)
  • best compressive strength
  • High electrical resistance
  • large dielectric constant


Chemical properties

Crystal structure hexagonal
chemical formula Al2O3
Purity 99,997% Al2O3
Density 3,98g/cm

Physical properties

Hardness Mohs 9
Tensile strength 0,4 GPa at 25 °C
Compressive strength 2,1 GPa at 25 °C
Bending strength 0,6 GPa at 25 °C
Modulus of rupture 0,9 GPa at 25 °C

Electrical properties

Specific resistance 1011 Ohm/cm at 500°C
106 Ohm/cm at 1000°C
103 Ohm/cm at 2000°C
Dielectric strength 480 kV cm-1 (60 Hz)
Dielectric loss index 0.000030 parallel to C axis (C-plane)
0.000086 perpendicular to C axis (A-plane)

Thermal conductivity

Thermal expansion 6.6 x 10-6 °C-1 (20-50 °C), parallel to C axis
5.0 x 10-6 °C-1 (50°C), perpendicular to C axis
Thermal capacity 0.08 cal cm-1 s-1 °C-1 (25°C)
Specific heat 0.18 cal g-1 °C-1 (25°C)

Optical properties

Refractive index: 1,8 (@ 0,3μ), 1,6 (@5μ)
Optical transmission: to 97%, in the range 0.15 – 6 μm

Thermal properties

Application temperature 2000 °C
Melting point 2053 °C


  • Protection window / safety glasses
  • Fiber e.g. for medical
  • Wafer 2″ – 6″ for LEDs
  • Lenses for endoscopy
  • Protection tubes for thermocouples
  • Sight glasses
  • Watch glass
  • Components in laser technology
  • Analytical and plasma technology
  • Tubes for high pressure sodium lamps
  • Wear resistant components
  • Nuclear magnetic resonance spectroscopy / NMR spectroscopy
  • IR-/UV-sensors
  • Laboratory equipment, laboratory glassware
  • Medical instruments
  • Implants