“Mixed oxide ceramics” generally refers to the ZTA (zirconia toughened alumina) material group. Alumina and zirconia are mixed in different ratios. A rather common ratio is 20 % ZrO2 and 80 % Al2O3. This material is fired at temperatures between 1,500° and 1,600° C.
Adding zirconia to alumina increases both resistance to fracture and strength of the material. The properties can be improved using so-called “transformation toughening”.
Transformation toughening elevates crack resistance. Crack extension causes residual compressive stress in the material, stopping cracks or splitting them into smaller, less dangerous ones.
The material properties vary depending on the mixing ratios. Basically, this material variant combines the hardness of Al2O3 and the toughness of ZrO2 :
- Good tribological properties
- Very high strength with high hardness
- Very good corrosive resistance
- High fracture toughness
- High wear resistance
- Good surface condition
Mixed oxides have proved efficient in mechanically highly stressed components such as sliding bearings and pump shafts.