Dielectric, ferroelectric, piezoelectric properties and impedance analysis of nonstoichiometric (Bi0.5Na0.5)0.94+xBa0.06TiO3 ceramics

Lead-free piezoelectric ceramics (Bi0.5Na0.5)0.94+xBa0.06TiO3 (x = −0.01, 0, 0.01, 0.02) were prepared via the solid-state reaction method. The effects of (Bi0.5Na0.5)2+ nonstoichiometry on the structure and electric properties of the ceramics were studied. All of the prepared ceramics exhibited single-phase perovskite structures. The mean grain size of the ceramics decreased with increasing (Na0.5Bi0.5)2+ content. The values of the activation energy obtained via impedance analysis were 0.99, 1.05, 1.16, and 1.52 eV for the ceramics with x = −0.01, 0, 0.01, and 0.02, respectively. The poled ceramics with x = −0.01 and 0 exhibited three dielectric anomalies at temperatures corresponding to Td, TRE, and Tm in the dielectric constant-temperature curves. By contrast, the anomaly at TRE disappeared for the ceramics with x = 0.01 and 0.02. The ceramic with x = 0.01 exhibited the highest remanent polarization (Pr = 37.2 μC/cm2) and highest piezoelectric constant (d33 = 137 pC/N).