Optimized physical properties of [001]-textured (Na, K)NbO₃-based lead-free piezoceramics for high power piezoelectric energy harvesters

The output power of piezoelectric energy harvesters is influenced by the k_p and d₃₃ × g₃₃ of the piezoceramics. The untextured 0.96(Na_0.5K_0.5)(Nb_1−xSb_x)O₃-0.01CaZrO₃-0.03(Bi_0.5Ag_0.5)ZrO₃ [NK(N_1−xS_x)-CZ-BAZ] exhibited a low k_p and d₃₃ × g₃₃ owing to its small d₃₃ and large ϵ^T₃₃/ϵ₀. The [001]-textured x = 0.01 composition exhibited an enhanced k_p (0.73) and d₃₃ × g₃₃ (32.2 × 10⁻¹² m² N⁻¹) owing to the increased d₃₃ and decreased ϵ^T₃₃/ϵ₀. The domain of the textured NK(N_1−xS_x)-CZ-BAZ changed from microdomains to nanodomains and polar nanoregions with an increasing x, and the altered domain structure affected the piezoelectric properties of the samples. The harvester fabricated using the [001]-textured x = 0.01 composition exhibited high power (2.7 mW) and a large power density (6.72 mW cm⁻³), which is similar to the largest power density obtained from harvesters fabricated using NKN-related ceramics. Therefore, the [001]-textured NK(N_0.99S_0.01)-CZ-BAZ is a promising option for application in harvesters, and the [001]-texturing technique proves to be an efficient method for developing piezoceramics for use in harvesters.