Sapphire Material:

Physical properties

Crystal Structure:            Rhombohedra Hexagonal Single crystal
Chemical composition:    Al2O3
Purity:                           99.99%
Specific gravity:              3.99 - 3.98

Mechanical properties

Hardness:                      Mohs 9, Knoop =1700kg/mm2
Modulus of elasticity:      3.5X10⁶ to 3.9X10⁶kg/cm2
Compressive strength:     2.1X10⁴ kg/cm2
Tensile Strength:            1.9*10³ kg/cm2

Thermal properties

Melting Point:                 2050?
Softening Point:              1800?
Specific Heat:                 0.18 ?at 25??
Thermal Expansion:         6.7*10^-6 ?C-axis 5.0*10^{-6 ?} C-axis

Chemical properties

Acids and alkalis attack:    not attached by acid or alkalis, attacked by HF at 300?

Electrical properties

Dielectric Constant:          7.5 to 10
Electrical Resistivity:         10¹¹O/cm at 500?, 10⁶O/cm at 1000?, 10³O/cm at 2000?,

Optical properties

Refractive Index :              1.769 // C-axis,1.760 ± C-axis   at 0.5893µm
Visible Light:                    Excellent
Infrared:                           85% 0.75 - 4µm, 70% 4.7µm, 50% 5.2µm
Ultraviolet:                        80% 0.4-0.3µm, 60% 0.28µm, 50% 0.2µm