Direct observation of ferroelastic domain switching in polycrystalline BaTiO3 using in situ neutron diffraction

The extent and nature of ferroelastic re-orientation in a BaTiO3 ceramic under compressive stresses up to 150 MPa were studied using strain gauges and in-situ neutron powder diffraction. At ≥10 MPa during the first loading, the unpoled crystals shows ferroelastic re-orientation. By 80 MPa ∼12% of the material oriented for diffraction has switched. Nearly half of the switched material reverts to its original orientation upon relaxation of the load, leaving 7% permanently switched. Successive load cycles have little further effect. It is unlikely that the ferroelasticity observed here makes a significant contribution to toughening as it saturates at relatively low stresses, such as exist only in the outer region of the process zone.