Influence of electric field on the ultrasound velocity in PZT ceramics

The paper deals with the influence of the electric bias field on the ultrasound velocity of various samples of Pb(ZrxTi1−x)O3 (PZT) ceramics. The ultrasonic velocities were measured on commercial types of PZT ceramics as APC 841, APC 850, and APC 856, at room temperature. The comparison of the ultrasound velocities dependence on electric bias field was made for poled/unpoled soft ceramics. The ultrasonic pulse-echo technique was used in our experiment. The ultrasonic system is based on Matec Instruments, Inc. modules. The time domain response was recorded and time of flight between echoes was directly measured by digital oscilloscope, type Agilent 54622D. The high bias field was applied on disk samples by the high voltage amplifier type Trek 610D, using a special setup and sample holder. The sound velocity was found to change drastically near the coercive field for a PZT ceramics, where the velocity of longitudinal waves decreases with an increasing field while the velocity of shear waves increases, which is caused by the change of the elastic anisotropy under influence of the depolarization field. The consequent change of the piezoelectric contribution to effective elastic constant decreases the velocity of longitudinal waves and at the same time increases the velocity of shear waves around the coercive field.