Origin of high electromechanical properties in (K,Na)NbO3 -based lead-free piezoelectrics modified with BaZr O3

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)O3. 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.