Recent Progress on Defect Dipoles Characteristics in Piezoelectric Materials

Defect dipoles which have pronounced effects on properties of piezoelectric materials can be introduced either by partially modifying with acceptor impurities or volatizing of cation elements in perovskite lattice during sintering. The formation mechanism of defect dipoles and responses under external fields were reviewed in the present paper.Besides,the main physic mechanisms of ferroelectric aging,hysteresis loop abnormalities and electroshapememory effects in piezoelectric materials were discussed in detail from the defect dipoles viewpoints.Based on a defect mediated reversible domain switching mechanism,large recoverable electro-strain,as well as constricted hysteresis loops were obtained in unpoled aged ferroelectric crystals and/or ceramics,which indicated that aging was not always a detrimental effect,and may be promising for future novel applications.Furthermore,the defect dipole relaxation process was briefly described and the development trends of the high reliability piezoelectric actuators were proposed.