Electric-field-induced phase transitions in co-doped Pb(Zr _1-xTi_x)O₃ at the morphotropic phase boundary

The strain- and polarization-electric field behavior was characterized at room temperature for Pb0.98Ba0.01(Zr_1-xTi_x)0.98Nb 0.02O₃, 0.40 x 0.60. The investigated compositions were located in the vicinity of the morphotropic phase boundary, giving insight into the influence of crystal structure on the hysteretic ferroelectric behavior. The remanent strain of particular compositions is shown to be larger than theoretically allowed by ferroelectric switching alone, indicating the presence of additional remanent strain mechanisms. A phenomenological free energy analysis was used to simulate the effect of an applied electric field on the initial equilibrium phase. It is shown that electric-field-induced phase transitions in polycrystalline ferroelectrics can account for the experimental observations. The experimental and simulation results are contrasted to neutron diffraction measurements performed on representative compositions in the virgin and remanent states.