Crystalline Structure

Rhomboedral Hexagonal Single Crystal

Composition

AI₂O₃

Purity

99.99%

Cleavage

Conchoidal

Density

3.99-3.98 g/cm³

Disclosation Density

10⁹-10⁸/m²

Melting Point

2320K

Softening Point

2070K

Specific Heat

7.5*10² J/Kg*K at 300K

Thermal Conductivity

40W/m*K ┴ at 300K

Thermal Expansion

6.2*10^-6/K// C-axis 5.4*10^-6/K ┴ C-axis

Hardness

Mohs9 Knoop 2200 face // C-axis,knoop 1800 face ┴ C-axis

Youngs Modulus

4.4*10¹¹ pa at 300K

Modulus of Rupture

4.0*10⁸Pa at 300K

Compressive Strength

2.1*10⁹Pa at 300K

Tensile Strength

1.9*10⁸Pa at 300K

Poissons constant

0.30

Acids and alkalis attack

0 to 570K

Porosity

0

Dielectric Constant

10.6 electric field // C-axis at 300K,8.6 electric field ┴ C-axis at 300K

Electrical Resistivity

10⁹Ω*m at 770K,10⁴Ω*m at 1270,10Ω*m at 2270K

Refractive Index n_D at 0.5893μm

1760 face // C-axis , 1.769 face ┴ C-axis

Dispersive Power(n_F-n_C)

0.011 λ_f=0.4861μm,λ_c 0.6563μm

Transmission,Disc Thickness

1 mm

-Visible Light

Excellent

-Infrared

85%0.75-5μm,70% 5.5μm,50% 6μm

-Ultraviolet

80%0.4-0.3μm,60% 0.28μm,50% 0.2μm