Zirconium Oxide (ZrO₂ ) 

Zirconia is known for its good mechanical properties in combination with a high hardness and chemical stability. It is one of the few ceramic materials, which is not brittle. It is used in knives, scissors, and springs and finds more and more industrial applications in e.g. pumps.

Although it translates from the alpha into the gamma phase at approx 1200°C, causing the material to change in dimensions, it can be stabilized by doping it with yttrium. (Yttrium stabilised zirconia).