Contribution of (Bi0.45Y0.05)Na0.5ZrO3 to induced multiphase coexistence and enhanced piezoelectric properties of K0.5Na0.5NbO3 lead-free ceramics

In this study, new lead-free piezoelectric ceramics (1 −  x )(K 0.5 Na 0.5 )NbO 3 (KNN)– x (Bi 0.45 Y 0.05 )Na 0.5 ZrO 3 (BYNZ) were prepared using the conventional solid-state method, and the relation between the doping amount of (Bi 0.45 Y 0.05 )Na 0.5 ZrO 3 and its structural and electrical properties was investigated. Material characterization and structural analyses conducted using X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy revealed that KNN–BYNZ ceramics formed single perovskite structures at 0 ≤  x  ≤ 0.05 and a polycrystalline phase boundary (PPB) for the coexisting orthorhombic and tetragonal phases at 0.03 ≤  x  ≤ 0.05. The ceramics exhibited desirable electrical properties at  x   = 0.04 ( d 33  = 305 pC/N, k p  = 45.8 %, ε r  = 1316, tanδ  = 2.4 %, T c  = 332 °C, P r  = 28.2 μC/cm 2 , and E c  = 1.07 kV/mm). These findings reveal that the introduction of BYNZ enables the effective formation of a PPB in the KNN-based ceramics to improve their electrical properties, and they exhibit potential for replacing lead-based piezoelectric ceramics in the market.