Aluminium oxide vs Zirconia
Aluminium oxide and Zirconia are genuine alternatives to one another — a choice somebody actually makes — and differ on 3 measured properties, density most clearly.
Aluminium oxide vs Zirconia
Aluminium oxide
Al2O3
Industrial alumina — the refined intermediate between bauxite and aluminium metal, and a major ceramic in its own right.
Zirconia
ZrO2
A ceramic that resists cracking by changing crystal structure at the crack tip — and a convincing diamond substitute in its cubic form.
| Property | Aluminium oxide | Zirconia |
|---|---|---|
| Density | 3.987 g/cm³ | 5.68–6.1 g/cm³ higher |
| Melting point | 2072 °C | 2715 °C higher |
| Mohs hardness Only one of the two has a figure we can stand behind, so there is nothing to compare. | Not known | 8–8.5 |
| Molar mass | 101.96 g/mol | 123.22 g/mol higher |
| Refractive index Only one of the two has a figure we can stand behind, so there is nothing to compare. | Not known | 2.15–2.18 |
Choosing between them
Zirconia is recorded as a substitute for Aluminium oxide — stronger.
What it gives up: Several times the price, twice the density, and a much lower thermal conductivity — which matters wherever heat has to leave.
In this application, on the evidence cited above.