# Hafnia (Hafnium Oxide, HfO_{2})

Hafnia is an oxide-based engineering ceramic. It has the highest density among oxide-based engineering ceramics. In addition, it has the lowest heat capacity and a very low thermal conductivity. The graph bars on the material properties cards below compare hafnia 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.

## Thermal Properties

Maximum Temperature: Mechanical

2800 *°C* 5070 *°F*

Melting Onset (Solidus)

2900 *°C* 5250 *°F*

Specific Heat Capacity

120 *J/kg-K* 0.029 *BTU/lb-°F*

Thermal Conductivity

1.1 *W/m-K* 0.64 *BTU/h-ft-°F*

Thermal Expansion

6.0 *µm/m-K*

## Other Material Properties

Density

9.7 *g/cm ^{3}* 610

*lb/ft*

^{3}Elastic (Young's, Tensile) Modulus

57 *GPa* 8.3 *x 10 ^{6} psi*

Electrical Resistivity Order of Magnitude

9.0 *10 ^{x} Ω-m*

## Common Calculations

Stiffness to Weight: Axial

3.3 *points*

Stiffness to Weight: Bending

13 *points*

Thermal Diffusivity

0.95 *m ^{2}/s*

## Followup Questions

## Further Reading

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