The Role of Powder Calcination Conditions in the Sintering Behaviour of Calcined ZrO2 Powders

Precipitation of hydrous zirconia and its thermal decomposition represent the simplest method for the preparation of ultrafine zirconia powders. These powders are now widely used either in unstabilized form for toughening various ceramic matrices (so-called zirconia toughened ceramics) (1), or they are used for the production of tetragonal zirconia ceramics (2), containing a few % of Y2O3 or CeO2 as stabilizing agent, which also reduces ZrO2 grain growth during sintering. Therefore the crystallization of hydrous zirconia as well as the occurence and stability of the transitional metastable tetragonal (mt) phase, have been rather extensively investigated, but they are still not completely understood (3–10). Besides, the relationship between powder processing and powder characteristics, as well as their influence on the densification behaviour and microstructure of sintered material seem to be of great importance.