FERROELASTIC PROPERTIES OF LEAD-ZIRCONATE-TITANATE CERAMICS

To increase the reliability of multilayer actual:ors, calculation of t he mechanical stress inside the device during operation is important, This paper shows that the small-signal value of the elastic constant s is not sufficient to describe the complicated behavior of lead zircon ate titanate (PZT) ceramics. Therefore, compressive strain and depolar ization have been measured as a function of large-signal stress applie d parallel to the poling direction, The nonlinear dependence of the st rain and depolarization can clearly be explained by domain processes, Soft and hard PZT ceramics have been investigated. In hard PZT, domain switching appears at higher stresses than in soft PZT, Moreover, in h ard PZT, the domains partly switch back during unloading, The critical stress (coercive stress) necessary for a domain-switching process sho ws a dependence on the Zr:Ti ratio that is quite similar to the depend ence of the electric coercive field, The influence of an electric fiel d applied parallel to the poling direction and superimposed on the com pression experiment also has been examined, The coercive stress depend s linearly on the electric field, The linear coefficient of this relat ion is given by the ratio of depolarization to compressive strain caus ed by domain switching.