“…Potassium sodium niobate (KNN)-based piezoelectric materials are considered to be one of the most likely systems to replace lead-containing piezoelectric materials owing to their excellent piezoelectric properties, environmental friendliness, high Curie temperature, mechanical quality factors, etc. [4][5][6][7][8][9][10][11][12][13] Piezoelectric single crystals and ceramics are common piezoelectric materials, but in the same composition, piezoelectric single crystals generally exhibit higher piezoelectric properties than ceramics made of polycrystalline particles. For example, the piezoelectric coefficient (d 33 ) of normal Na 0.5 Bi 0.5 TiO 3 -BaTiO 3 ceramics is about 100-150 pC N −1 , 14,15 but Na 0.5 Bi 0.5 TiO 3 -BaTiO 3 single crystals show a higher piezoelectric coefficient.…”