Effect of zirconium non-stoichiometry on phase structure and electrical properties of (K,Na)(Nb,Sb)O3-(Bi,Na)ZrO3 ceramics

Abstract As dopant, (Bi0.5Na0.5)ZrO3 can significantly enhance electrical properties of KNN ceramics. However, certain issues in (K,Na)(Nb,Sb)O3-(Bi,Na)ZrO3 ceramics are still not well understood, one of which is the effect of zirconium non-stoichiometry on its electrical behaviors. Herein, 0.96(K0.48Na0.52)(Nb0.96Sb0.04)O3-0.04(Bi0.5Na0.5)Zr1+xO3 (x = -0.02, -0.05, 0, 0.02, 0.05, 0.08) ceramics were prepared by pressureless sintering. The effect of zirconium ions non-stoichiometry on phase structure, domain structure and electrical behavior was explored. All ceramics had a pure perovskite structure with rhombohedral phase. The piezoelectric coefficient d33, remanent polarization (Pr) and coercive electric field (EC) reach the maximum (d33 = 351 pC/N, EC = 10.77 kV/cm and Pr = 24.26 μC/cm2) with x = 0.05. The results showed that the electric properties of the studied system can be significantly affects by trace zirconium. The appropriate excess of zirconium element would increase the concentration of oxygen vacancy, which could enhance the pinning effect of the domain walls and increase EC and Pr correspondingly. The domain structure characterized by PFM technology further confirms the macroscopic results. Moreover, a defect switching model was proposed to probe into the effect of defects on their performances. Thus, it is believed that this work would provide a new strategy for further optimizing the comprehensive properties of binary or multivariate KNN-based ceramics.