Ferroelectric polycrystals: Structural and microstructural levers for property-engineering via domain-wall dynamics

Ferroelectrics have a spontaneous electrical polarization that is arranged into domains and can be reversed by an externally-applied field. This high versatility makes them useful in enabling components such as capacitors, sensors, and actuators. Key parameters to tune their dielectric, piezoelectric, and electromechanical performance are the domain structure and the dynamic of the domain walls. In fixed compositions, this is often realized by chemical doping. In addition, structural and microstructural parameters, such as grain size, degree of crystallographic texture and porosity play a key role. An important step forward in the field was the fundamental understanding of the link between the local electric and mechanical driving forces and domain wall motion. Here, the impact of crystal structure and microstructure on these driving forces is reviewed and an engineering toolbox is introduced. An overview of advances in the understanding of domain wall motion on the micro- and nanoscale is provided and discussed in terms of the macroscopic functional performance of polycrystalline ferroelectrics/ferroelastics. In addition, a link to theoretical and computational models is established. The review concludes with a discussion about beyond state-of-the-art characterization techniques, new approaches, and future directions toward non-conventionally ordered ferroelectrics for next-generation nanoelectronic and energy-storage applications.