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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. It has six common variants, each represented as a separate material. The material properties section shows ranges encompassing all variants. To see the details of each variant on a separate page, follow the links in the Variant Materials section further below.

Mechanical Properties

Graph bars compare alumina to other oxide-based engineering ceramics (top) and the entire database (bottom).

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 3340 to 6540 psi-in1/2

Knoop Hardness

960 to 1660

Poisson's Ratio

0.22 to 0.24

Strength to Weight Ratio

57 to 72 kN-m/kg

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

7.7 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

0.00048 to 0.0013

Electrical Resistivity Order of Magnitude

6.3 to 14 10x Ω-m

Other Material Properties

Density

3.5 to 4.1 g/cm3 220 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 Diffusivity

4.4 to 8.6 m2/s

Thermal Expansion

6.7 to 8.2 µm/m-K

Followup Questions

Variant Materials

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