“…Consequently, exploration of high-performance lead-free piezoelectric materials has continued to increase in recent years. [5][6][7] For example, perovskite-based materials, including BaTiO 3 -based, [8][9][10][11][12][13][14] (Bi, Na)TiO 3 -based, [15][16][17][18][19] and (K, Na)NbO 3 -based 5,[20][21][22][23] materials, have been widely reported as substitutes for PZT-based materials. However, the inferior piezoelectric properties of these lead-free materials have prevented their practical application.…”