GENERAL

Chemical Formula

Al2O3

Crystal Stucture

Hexagonal System ((hk o 1)

Unit Cell Dimension

a=4.758 A,A c=12.991 A, c:a=2.730

PHYSICAL

Metric

Density

3.98 g/cc

Hardness

1525 - 2000 Knoop,  9 mhos

Melting Point

2310 K (2040° C)

STRUCTURAL

Tensile Strength

275 MPa to 400 MPa

at 20°

400 MPa

at 500° C

275 MPa

at 1000° C

355 MPa

Flexural Stength

480 MPa to 895 MPa

Compression Strength

2.0 GPa (ultimate)

MODULUS

Young's Modulus, E

345 GPa

(Modulus of Elasticity)

Bulk Modulus, k

250 GPa

(Modulus of Compression)

Shear Modulus, G

145 GPa

(Modulus of Rigidity)

MOR

350 MPa to 690 MPa

(Modulus of Rupture)

Poisson's Ratio

Sapphire is anisotropic.
 It is orientation dependent.

THERMAL

Thermal Conductivity

at 0° C

46.06 W/(m · K)

(60° orientation)

at 100° C

25.12 W/(m · K)

at 400° C

12.56 W/(m · K)

Specific Heat at 20° C

0.187 cal/(g · °C)

Heat Capacity

at 20° C

18.63 cal/ (mole · °C)

at 1000° C

29.86 cal/ (mole · °C)

Thermal Expansion Coefficient

20° to 50° C

5.8 x 10-6/ °C

(60 degree orientation)

20° to 500°C

7.7 x 10-6/ °C

ELECTRICAL

Frequency

E l to C axis

Dielectric Constant

Loss Tangent

1 MHz

9.39

0.0001

3 GHz

9.39

<0.0001

8.5 GHz

9.39

<0.00002

Volume Resistivity at 25 °C

1014 ohm · cm