Ceramic knife

Cooling to the monoclinic phase after sintering causes a large volume change, which often causes stress fractures in pure zirconia.

Additives such as magnesia, calcia and yttria are used in manufacturing the knife material to stabilize the high-temperature phases and minimize this volume change.

The highest strength and toughness is produced by the addition of 3 mol% yttrium oxide yielding partially stabilized zirconia.

Since ceramics are brittle, blades may break if dropped on a hard surface, although improved manufacturing processes have reduced this risk.

Several brands offer either a black-coloured or a designed blade made through an additional hot isostatic pressing step, which increases toughness.