Invited
TIME-RESOLVED X-RAY DIFFRACTION REVEALS THE HIDDEN MECHANISMS OF ENHANCED PIEZOELECTRIC ACTIVITY IN FERROELECTRICS

Piezoelectrics are implemented in the great number of devices, such as sensors, actuators and frequency generators. Although a piezoelectric does not have to be ferroelectric, coexistence of piezo- and ferroelectricity can enhance the piezoelectric coefficient by two orders of magnitude. The connection between the piezoelectricity and the ferroelectricity is still debated, in particular due to severe mixing of purely “intrinsic” (atomic) and “extrinsic” (mesoscopic, e.g. domain-wall motion) effects.

Here, we present in-situ time resolved X-ray diffraction for advanced characterization of the origin of piezoelectricity in ferroelectrics. The technique measures intensity of X-ray diffraction as a function of time and dynamically applied electric field. It benefits from the ability to follow bulk lattice parameter(s), domain sizes and atomic structure during polarization reversal.

As the case example, we will demonstrate the mechanisms of enhanced piezoelectric activity in uniaxial Sr_0.5Ba_0.5Nb₂O₆ (SBN) ferroelectric [1]. It suggests that piezoelectricity may be enhanced during the process of electric field-induced polarization reversal. In turn, it was established that polarization in SBN may be reverted via two different routes: without and with nucleation of small ferroelectric domains. The first route passes over the strain minimum while the second route passes over the strain maximum. This second route shows a dramatic enhancement of piezoelectricity in the form of the correlation between the domain sizes and their lattice parameter. We believe that this route creates a novel roadmap for designing materials with enhanced piezoelectricity.

The application of time-resolved X-ray diffraction for the investigation of perovskite-based (piezo-) ferroelectrics will be also shown.

[1] S. Gorfman, H. Choe, V. V Shvartsman, M. Ziolkowski, M. Vogt, J. Strempfer, T. Łukasiewicz, U. Pietsch, and J. Dec, Phys. Rev. Lett. 114, 97601 (2015).