Alumina (Aluminum Oxide, Al2O3)

Alumina is a oxide-based engineering ceramic material.

It has six common variants, each represented as a separate material.

Material Properties

Compressive (Crushing) Strength1920 to 2750 MPa (280 to 400 x 103 psi)

Density3.5 to 4.1 g/cm3 (220 to 260 lb/ft3)

Dielectric Constant (Relative Permittivity)7.9 to 11

Dielectric Strength (Breakdown Potential)8.9 to 12 kV/mm (0.35 to 0.47 V/mil)

Elastic (Young's, Tensile) Modulus220 to 370 GPa (32 to 54 x 106 psi)

Electrical Resistivity Order of Magnitude7 to 14 10x Ω-m

Flexural Strength260 to 430 MPa (38 to 62 x 103 psi)

Fracture Toughness3.7 to 7.2 MPa-m1/2

Knoop Hardness960 to 1660

Maximum Thermal Shock200 to 300 °C (390 to 570 °F)

Melting Onset (Solidus)2040 °C (3700 °F)

Poisson's Ratio0.22 to 0.24

Specific Heat Capacity870 to 940 J/kg-K

Strength to Weight Ratio60 to 71 kN-m/kg

Tensile Strength: Ultimate (UTS)210 to 290 MPa (30 to 42 x 103 psi)

Thermal Conductivity14 to 30 W/m-K

Thermal Diffusivity3.9 to 4.6

Thermal Expansion6.8 to 8.2 µm/m-K

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