Chemical formula:

Al₂O₃

Growing method:

Kyropoulos

Structure:

hexagonal
a = b = 4.77 A
c = 13.04 A

Thermal

Melting temperature:

2040 °C

Linear expansion coefficient:

6.7 x 10^-6 / °C parallel to С axis
5.0 x 10^-6 / °C perpendicular to С axis

Thermal conductivity:

46.06 W/m °K (0°C)

Mechanical

Density:

3.98 g/cm³

Hardness:

Mohs: 9
Knoop: 1800 daN/mm² parallel to С axis
2200 daN/mm² perpendicular to С axis

Tensile strength:

400 MPa/mm² (25°C) 275 MPa/mm² (500°C) 345 MPa/mm² (1000°C)

Flexural strength:

35 to 39 daN/mm²

Compression stress:

2.0 GPa

Young's modulus

3.6 x 10⁴ to 4.4 x 10⁴ daN/mm²

Electric

Dielectric permeability:

9.3 (10³ - 10⁹ Hz, 25°C) perpendicular to С axis
11.5 (10³3 - 10⁹ Hz, 25°C) parallel to С axis

Specific resistivity:

10¹⁶ ?/cm (25°C)
10¹¹ ?/cm (500°C)
10⁶ ?/cm (1000°C)