Coercive force and 90° domain wall motion in ferroelectric PLZT ceramics with square hysteresis loops

The polarization reversal of some tetragonal-phase PLZT ceramics is studied. The results are explained in terms of 90° domain wall motions. A reported theory originally derived for rhombohedral-phase PLZT 6/65/35 ceramics is shown to be applicable to tetragonal-phase PLZT ceramics also by introducing the remanent degree of 90° domain alignment γ90. As a result, the calculation of coercive force is possible for various PLZT compositions considering the interaction of 90° domain wall motions and reacting forces established by the internal stress state of ferroelectric ceramics. The frequency dependence of coercive force and measurements of switching strain, including depolarization data obtained from either mechanically or electrically produced external forces, confirm the interpretation of predominantly occuring 90° reorientations and are consistent with the extended theory.