Domain Switching as a Toughening Mechanism in Tetragonal Zirconia

Evidence for a toughening contribution from domain switching, a deformation mode akin to twinning, has been sought in uniaxial tension and compression, biaxial compression, and on the fracture surfaces of several tetragonal zirconia polycrystalline (TZP) ceramics. Only in biaxial compression was domain switching found. In other cases, textures of both the tetragonal and monoclinic phases were due to stress coupling with transformation shear strain. The lower bound of the critical stress for domain switching is placed at the bend strength of TZP, which can exceed 1000 MPa. Although thermal activation may lower the critical stress sharply, at lower temperatures, domain switching is not likely to be an important toughening mechanism.