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Alumina (Aluminum Oxide, Al2O3)

Alumina is an oxide-based engineering ceramic. It can have a fairly high thermal conductivity and a moderately high heat capacity relative to other oxide-based engineering ceramics.

The properties of alumina include six common variations. The property values on this page show ranges across all of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare alumina to other oxide-based engineering ceramics (top) and the entire database (bottom). The length of each bar shows the given value as a % of the largest value in the relevant set.

Mechanical Properties

Compressive (Crushing) Strength

1920 to 2750 MPa 280 to 400 x 103 psi

Elastic (Young's, Tensile) Modulus

220 to 370 GPa 32 to 54 x 106 psi

Flexural Strength

260 to 430 MPa 38 to 63 x 103 psi

Fracture Toughness

3.7 to 7.2 MPa-m1/2 3.3 to 6.5 x 103 psi-in1/2

Knoop Hardness

960 to 1660

Poisson's Ratio

0.22 to 0.24

Tensile Strength: Ultimate (UTS)

210 to 290 MPa 30 to 42 x 103 psi

Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 Hz

8.0 to 9.0

Dielectric Constant (Relative Permittivity) At 1 MHz

7.8 to 11

Dielectric Strength (Breakdown Potential)

8.9 to 12 kV/mm 0.35 to 0.48 V/mil

Electrical Dissipation At 1 Hz

0.00031 to 0.0011

Electrical Dissipation At 1 MHz

0.00049 to 0.0013

Electrical Resistivity Order of Magnitude

6.2 to 14 10x Ω-m

Other Material Properties

Density

3.4 to 4.1 g/cm3 210 to 260 lb/ft3

Maximum Thermal Shock

200 to 300 °C 380 to 580 °F

Melting Onset (Solidus)

2040 °C 3700 °F

Specific Heat Capacity

870 to 940 J/kg-K 0.21 to 0.22 BTU/lb-°F

Thermal Conductivity

14 to 30 W/m-K 8.2 to 17 BTU/h-ft-°F

Thermal Expansion

6.7 to 8.2 µm/m-K

Common Calculations

Stiffness to Weight: Axial

35 to 53 points

Stiffness to Weight: Bending

57 to 62 points

Strength to Weight: Axial

14 to 23 points

Strength to Weight: Bending

19 to 28 points

Thermal Diffusivity

3.7 to 10 m2/s

Thermal Shock Resistance

4.9 to 14 points

Followup Questions

Further Reading

ASTM D2442: Standard Specification for Alumina Ceramics for Electrical and Electronic Applications

Ceramic and Glass Materials: Structure, Properties and Processing, James F. Shackelford and Robert H. Doremus (editors), 2008

IEC 60672-3: Ceramic and glass-insulating materials - Part 3: Specifications for individual materials