Direct observation of pulse poling effect on reversible 90° domain wall motion in tetragonal Pb(Zr,Ti)O<sub>3</sub> thin films

We investigated the effects of the pulse poling process on macroscopic ferroelastic domain structures in (100)/(001)-oriented Pb(Zr 0.44 Ti 0.56 )O 3 films.The poling process consisted of an applied electric field square waveform for poling cycles (10 0 -10 7 cycles) combined with triangular waveforms for polarization-electric field and strain-electric field measurements.The remanent polarization (P r ) and the inverse piezoelectric coefficient (d 33, f ) were enhanced at 10 3 poling cycles but decreased with further increases in poling cycles.After 10 3 poling cycles, the 90 domain switching behavior was directly observed via in situ X-ray diffraction (XRD).The results showed a 4% change in the volume fraction of the c-domain (V C ) during the application of an electric field of +150 kV/cm.The 90 domain structure was altered by the poling process, contributing to increased electric field-induced strain.However, in situ XRD results after 10 7 poling cycles indicated only slight changes in V C under an applied electric field, with degraded P r and d 33, f .The degradation of d 33, f values by pulse poling is partly due to the reduced contribution of ferroelastic 90 domain switching.