Neutron diffraction observations of ferroelastic domain switching and tetragonal-to-monoclinic transformation in Ce-TZP

In-situ neutron diffraction has been used to study the plastic deformation of a tetragonal zirconia polycrystal stabilized with 12 mol% ceria under compressive loads up to 1.6 GPa. The development of significant plastic strain in the ceramic has been found to be due to a combination of ferroelastic switching and the tetragonal-to-monoclinic phase transformation, both beginning at ∼1.2 GPa. Evidence of a strong coupling between the two phenomena is present. Both transitions are partially reversed on removal of the load. The linear elastic response of the a and c crystal axes of the parent tetragonal phase suggests that the ferroelastic switching occurs directly by a shear mechanism rather than via a cubic intermediate state. Anisotropic distortion of the tetragonal unit cell, as the critical stress is approached, gives some insight into the shear transformation mechanisms