Transformation Toughening of Zirconia Ceramics

Mg-partially stabilized zirconia (Birkby and Stevens, 1996). Reprinted with permission of Trans Tech Publication, Millersville, DA, USA. 

Nucleation and the growth of spindle-shaped tetragonal particles occur that are stable against transformation, even at room temperature. The metastable 

The classic Griffith-Orowan theory describes the relationship between the strength and toughness of brittle materials such as ceramics (Griffith, 1920 Orowan, 1949). In the simple basic equation of the theory, the stress to fracture Of is related to Young s elastic modulus E, the fracture energy y, and the critical crack length c, by  

As the crihcal stress intensity factor i hire stress becomes 

Indeed, the fCic values of PSZ are very much higher than those of other engineering ceramics, varying between 7 (CaO-PSZ with 3.3 mass% CaO), 9 (MgO-PSZ with 3.4 mass% MgO), 10 (Y2O3-PSZ with 8 mass% Y2O3) and 11 (Ce02- 

As the critical stress intensity factor (=fracture toughness) is Klc = ] IE y the fracture stress becomes 

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