High Piezoelectric and Mechanical Properties for (K,Na)NbO3-Based Textured Piezoceramics

(K,Na)NbO3-based ceramics are promising lead-free piezoelectrics due to their excellent piezoelectric coefficient (d33) and high Curie temperature (Tc), but their poor mechanical properties limit high-reliability applications. To address this issue, 0.97K0.5Na0.5Nb0.95Sb0.05O3-0.03Bi0.5Na0.5ZrO3-0.5%wtBiFeO3-xZrO2(KNNS-xZrO2) textured ceramics were developed. Excessive ZrO2 improved mechanical performance, while <001>-oriented samples exhibited strong piezoelectricity. At x = 0.01, the ceramics achieved high values in the KNN system: d33 ∼ 326 pC·N−1, Hv ∼ 8.46 ± 0.14 GPa, E ∼ 172 ± 4 GPa, and fracture toughness KIC ∼ 1.70 ± 0.09 MPa·m1/2. Based on these outstanding properties, a KNNS-0.01ZrO2 piezoelectric wristband was fabricated to monitor human heart rate, producing stable current signals under different motion states. This work provides insights for reliable piezoelectric sensors and actuators.