Improvement of piezoelectricity of (Na, K)Nb-based lead-free piezoceramics using [001]-texturing for piezoelectric energy harvesters and actuators

0.96(Na_0.5K_0.5)(Nb_0.93Sb_0.07)O₃−(0.04−x)BaZrO₃−x(Bi_0.5Ag_0.5)ZrO₃[NKNS−(0.04−x)BZ−xBAZ] ceramics are well textured along the [001] direction using 3.0 mol% NaNbO₃ seeds. The textured-NKNS−0.02BZ−0.02BAZ thick film has a rhombohedral-orthorhombic-tetragonal (R-O-T) structure with a large proportion of the O-R structure (> 80%). This specimen exhibits the largest values for d₃₃ (805 pC/N) and d₃₃ ×g₃₃ (29.5 ×10⁻¹² m²/N), which are the largest d₃₃ and d₃₃ ×g₃₃ values of NKN-based piezoceramics to date. It exhibits a large strain (0.17% at 4.0 kV/mm). Therefore, it is an outstanding piezoceramic material for piezoelectric energy harvesters (PEHs) and actuators. A PEH and actuator are fabricated using this specimen. The PEH shows a large power density (4.3 mW/cm³), which is the largest value among the PEHs produced by lead-free piezoceramics. The actuator exhibits a large acceleration (50.8 G) and displacement (3.9 mm), which are the best actuating properties among the actuators produced by lead-free piezoceramics. Therefore, texturing is an excellent technique for improving the piezoelectricity of NKN-based piezoceramics.