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

Abstract

After two decades of extensive research, selected lead-free piezoelectric materials based on the $(\mathrm{K},\mathrm{Na})\mathrm{Nb}{\mathrm{O}}_{3}$ (KNN) system exhibit excellent electromechanical properties that are comparable or even superior to those of $\mathrm{Pb}(\mathrm{Zr},\mathrm{Ti}){\mathrm{O}}_{3}$. 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 $(\mathrm{K},\mathrm{Na})\mathrm{Nb}{\mathrm{O}}_{3}$-based composition, modified with $(\mathrm{B}{\mathrm{i}}_{0.5}\mathrm{L}{\mathrm{i}}_{0.5})\mathrm{Ti}{\mathrm{O}}_{3}$ and different amounts of $\mathrm{BaZr}{\mathrm{O}}_{3}$. 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.