Enhanced thermal and cycling reliabilities in (K,Na)(Nb,Sb)O₃-CaZrO₃-(Bi,Na)HfO₃ ceramics

The thermal stability and fatigue resistance of piezoelectric ceramics are of great importance for industrialized application. In this study, the electrical properties of (0.99-x)(K_0.48Na_0.52)(Nb_0.975Sb_0.025)O₃- 0.01CaZrO₃-x(Bi_0.5Na_0.5)HfO₃ ceramics are investigated. When x = 0.03, the ceramics exhibit the optimal electrical properties at room temperature and high Curie temperature (T_C = 253 ℃). In addition, the ceramic has outstanding thermal stability (d₃^*₃ ≈ 301 pm/V at 160 ℃) and fatigue resistance (variation of P_r and d₃^*₃ ~10% after 10⁴ electrical cycles). Subsequently, the defect configuration and crystal structure of the ceramics are studied by X-ray diffraction, temperature- dielectric property curves and impedance analysis. On one hand, the doping (Bi_0.5Na_0.5)HfO₃ makes the dielectric constant peaks flatten. On the other hand, the defect concentration and migration are obviously depressed in the doped ceramics. Both of them can enhance the piezoelectrical properties and improve the temperature and cycling reliabilities. The present study reveals that the good piezoelectric properties can be obtained in 0.96(K_0.48Na_0.52)(Nb_0.975Sb_0.025)O₃-0.01CaZrO₃-0.03(Bi_0.5Na_0.5) HfO₃ ceramics.