NEUTRON-DIFFRACTION OBSERVATIONS OF FERROELASTIC DOMAIN SWITCHING ANDTETRAGONAL-TO-MONOCLINIC TRANSFORMATION IN CE-TZP

In-situ neutron diffraction has been used to study the plastic deforma tion of a tetragonal zirconia polycrystal stabilized with 12 mol% ceri a under compressive loads up to 1.6 GPa. The development of significan t plastic strain in the ceramic has been found to be due to a combinat ion of ferroelastic switching and the tetragonal-to-monoclinic phase t ransformation, both beginning at similar to 1.2 GPa. Evidence of a str ong coupling between the two phenomena is present, Both transitions ar e partially reversed on removal of the load, The linear elastic respon se 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.