Origin of high electromechanical properties in (K,Na)NbO3-based lead-free piezoelectrics modified with BaZrO3

After two decades of extensive research, selected lead-free piezoelectric materials based on the (K,Na)NbO3 (KNN) system exhibit excellent electromechanical properties that are comparable or even superior to those of Pb(Zr,Ti)O-3. The origin of the superior properties, however, remains insufficiently understood. Here, we establish a correlation between electromechanical properties and domain-wall dynamics for a prominent piezoceramic (K,Na)NbO3-based composition, modified with (Bi0.5Li0.5)TiO3 and different amounts of BaZrO3. This composition combines excellent piezoelectric properties, high fatigue resistance, and low leakage currents. Domain-wall dynamics were studied over a broad range of electric fields, combining subcoercive field and dynamic pulse measurements. We find that the enhanced electromechanical properties in these materials are caused by easier domain-wall movement. Besides providing insights into fundamental mechanisms of domain-wall dynamics in KNN-based materials, our results can serve as a future guidance for the design of high-performance KNN compositions.