Crystallographic features of the ferroelectric incommensurate phase in Pb(Zr_1-xTi_x)O₃

Crystallographic features of perovskite Pb(Zr_1-xTi_x)O₃ with x=0.03, 0.1, and 0.15 have been examined at various temperatures above room temperature by transmission electron microscopy. Among these oxides, the incommensurate phase was found to exist in x=0.03 and 0.10. In addition, the present data suggest that the incommensurate structure is developed in two steps. The first step is the formation of a microtwin structure, which is associated with the rotation of the oxygen octahedra involved in a crystal structure. The periodic array of antiphase boundaries for an antiferroelectric displacement of the Pb ions is introduced into the microtwin structure in the second step. The resultant structure can be identified as a discommensurate structure in the incommensurate phase of Pb(Zr_1-xTi_x)O₃.