"Zirconia – Ceramic steel". The title of the first scientific paper to highlight the possibilities offered by the "transformation toughening” mechanism which occurs in certain zirconia ceramics. Since the publication of this seminal work in 1975, considerable research, development, and marketing effort has been expended on this single material which offers the traditional ceramic benefits of hardness, wear resistance, and corrosion resistance, without the characteristic ceramic property of absolute brittleness.

Mechanical and Physical Properties

The fundamental properties of zirconia ceramic which are of interest to the engineer or designer are:

- High strength
- High fracture toughness
- High hardness
- Wear resistance
- Good frictional behaviour
- Non-magnetic
- Electrical insulation
- Low thermal conductivity
- Corrosion resistance in acids and alkalis
- Modulus of elasticity similar to steel
- Coefficient of thermal expansion similar to iron

The usual nomenclature used to describe zirconia ceramic alloys is as detailed below

- TZP tetragonal zirconia polycrystals
- PSZ partially stabilised zirconia
- FSZ fully stabilised zirconia
- TTC transformation toughened ceramics
- ZTA zirconia toughened alumina
- TTZ transformation toughened zirconia

Zirconia ceramics are used for manufacturing Extrusion dies, powder compacting dies, cutting tools, balls and seats for ball valves, thread and wire guides, pump seals, impellers and shaft guides, engine parts, oxygen sensors, fuel cells membranes,high temperature heaters for electric furnaces, bearings (e.g., bearings for submersible pumps).