CHANGE OF THE WEAK-FIELD PROPERTIES OF PB(ZRTI)O-3 PIEZOCERAMICS WITHCOMPRESSIVE UNIAXIAL STRESSES AND ITS LINKS TO THE EFFECT OF DOPANTS ON THE STABILITY OF THE POLARIZATIONS IN THE MATERIALS

The properties of several Pb(ZrTi)O-3 (PZT) piezoceramics under compre ssive uniaxial stresses were characterized. It was observed that uniax ial stresses have a marked effect on the soft PZT materials, including reducing the piezoelectric coefficients and depoling the samples at r elatively low stress levels. The effect of the uniaxial stresses on th e properties of hard PZT's is more complicated because the domain stru cture of the materials can be changed substantially without depoling t he samples. Therefore, under a compressive stress along the poling dir ection, the piezoelectric and electromechanical coupling factor can be increased markedly due to both the increased non-180 degrees domain b oundary motions and the deaging effect. In addition, the experimental results support the notion that the difference between a hard PZT and a soft PZT lies in the types of defects introduced by dopants. Immobil e defects create frustrations in the lattice and result in a soft beha vior, and mobile defects stabilize the polarization and produce a hard behavior.