[001]-texturing of (K, Na)NbO₃-based piezoceramics with a pseudocubic structure and their application to piezoelectric devices

0.96(K_0·5Na_0.5-zLi_z) (Nb_0·92Sb_0.08)O₃-0.04(Ca_0·5Sr_0.5)ZrO₃ [(KN_0.5-zL_z)NS-CSZ] piezoceramics (0 ≤ z ≤ 0.04) were aligned in the [001] orientation using 3% (in mole) NaNbO₃ templates with a large Lotgering factor (>97%). Their crystal structures transformed from the orthorhombic-pseudocubic (O[sbnd]P) structure to the orthorhombic-tetragonal-pseudocubic (O-T-P) structure with an increasing z. The P structure was interpreted as a rhombohedral R3m structure. The piezoelectricity of the compositions increased after [001]-texturing, and the enhancement was proportional to the O phase quantity. The composition (z = 0.03) exhibited the highest piezoelectric constant (d₃₃; 670 pC/N) and electromechanical coupling factor (k_p; 0.56). Piezoelectric energy harvesters were produced using the untextured and textured samples (z = 0.03). The textured harvester delivered a large power density of 26.6 mW/mm³, which was larger than that of the untextured harvester owing to the enhanced k_p and d₃₃ × g₃₃ of the textured piezoceramic. A multilayer actuator was produced using the textured sample (z = 0.03), and it exhibited a large acceleration (44.2 G) and displacement (±3,730 μm) at ±25 V. Therefore, the [001]-textured (KN_0.47L_0.03)NS-CSZ piezoceramic is suitable for piezoelectric energy harvesters and actuators.