Reduced sound velocity in PbZrO3 thin film during antiferroelectric to ferroelectric transition revealed by picosecond acoustics

The antiferroelectric-to-ferroelectric (AFE-FE) phase transition has attracted considerable attention due to its potential applications in high-strain transducers, thermal switching, and pulsed-power devices. To deepen our understanding of this transition and enable its functionalities, ultrafast dynamics, especially lattice dynamics of antiferroelectricity, are essential to be demonstrated. In this work, the picosecond acoustics technique is applied to measure the sound velocity of a high-quality PbZrO3 epitaxial thin film with a thickness of ∼110 nm, determining it to be 5879 ± 11 m/s. More importantly, our in situ measurements reveal a reduction in sound velocity of approximately 6% during the AFE-FE phase transition under an external electric field of ∼364 kV/cm at ambient conditions. This reduction can increase to about 12% with an elevated electric field of approximately 545 kV/cm. Additionally, we found that this field-induced ferroelectric phase is metastable and the recovery takes up to tens of hours at ambient conditions, indicating a memory effect of the field-induced state. These findings suggest that the AFE-FE phase transition in PbZrO3 thin films holds promise for applications in acoustic wave manipulation.