# 93-95% Purity Alumina (ASTM D2442 Type II, IEC 60672 Type C-786)

Type II alumina is a grade of alumina. It has the lowest strength compared to the other variants of alumina. The graph bars on the material properties cards below compare type II alumina to other oxide-based engineering ceramics (top) and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

## Mechanical Properties

Compressive (Crushing) Strength

2260 *MPa* 330 *x 10 ^{3} psi*

Elastic (Young's, Tensile) Modulus

270 *GPa* 40 *x 10 ^{6} psi*

Flexural Strength

320 *MPa* 46 *x 10 ^{3} psi*

Fracture Toughness

3.9 *MPa-m ^{1/2}* 3.6

*x 10*

^{3}psi-in^{1/2}Knoop Hardness

1120

Poisson's Ratio

0.22

Shear Modulus

120 *GPa* 18 *x 10 ^{6} psi*

Tensile Strength: Ultimate (UTS)

210 *MPa* 30 *x 10 ^{3} psi*

## Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 Hz

9.0

Dielectric Constant (Relative Permittivity) At 1 MHz

8.7

Dielectric Strength (Breakdown Potential)

12 *kV/mm* 0.48 *V/mil*

Electrical Dissipation At 1 Hz

0.00067

Electrical Dissipation At 1 MHz

0.00073

Electrical Resistivity Order of Magnitude

13 *10 ^{x} Ω-m*

## Other Material Properties

Density

3.7 *g/cm ^{3}* 230

*lb/ft*

^{3}Maximum Temperature: Mechanical

1550 *°C* 2820 *°F*

Maximum Thermal Shock

250 *°C* 480 *°F*

Melting Onset (Solidus)

2040 *°C* 3700 *°F*

Specific Heat Capacity

900 *J/kg-K* 0.22 *BTU/lb-°F*

Thermal Conductivity

19 *W/m-K* 11 *BTU/h-ft-°F*

Thermal Expansion

7.2 *µm/m-K*

## Common Calculations

Stiffness to Weight: Axial

41 *points*

Stiffness to Weight: Bending

59 *points*

Strength to Weight: Axial

16 *points*

Strength to Weight: Bending

21 *points*

Thermal Diffusivity

5.8 *mm ^{2}/s*

Thermal Shock Resistance

7.7 *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

Ceramics and Composites: Processing Methods, Narottam P. Bansal and Aldo R. Boccaccini (editors), 2012

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

Springer Handbook of Condensed Matter and Materials Data, W. Martienssen and H. Warlimont (editors), 2005