Textured (K,Na)NbO₃ ceramics with enhanced piezoelectric properties: High k_p, d₃₃, and Curie temperature

Lead-free (K,Na)NbO₃ (KNN) ceramics are eco-friendly and have a high Curie temperature. In this work, high-performance KNN ceramics were synthesized through the texturing method while simplifying the components. The results indicate that the KNN-3 textured ceramics exhibit excellent piezoelectric properties of d₃₃ = 315 pC/N, d₃₃* = 600 pm/V, and k_p = 0.74 without sacrificing the Curie temperature of 394 °C. Compared with those of the KNN ceramics prepared via the conventional solid-state reaction method (d₃₃ = 104 pC/N, k_p = 0.26), d₃₃ and k_p increase by approximately 203% and 185%, respectively. Such high d₃₃ and k_p values arise from a high texture degree (f) of 94%. Additionally, at 25 °C under an electric field of 35 kV/cm, the KNN-3 ceramic shows a maximum polarization (P_max) of 28.52 μC/cm² and a remanent polarization (P_r) of 25.69 μC/cm². At 120 °C under an applied field of 30 kV/cm, the ceramic also exhibited the strain (S) = 0.18% and strain hysteresis (H) ≈ 11.1%, demonstrating excellent ferroelectric properties. Moreover, the ceramic has a high density, good breakdown strength, and low dielectric loss.