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+x)Ba0.06TiO3 (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 T-d, T-RE, and T-m in the dielectric constant temperature curves. By contrast, the anomaly at T-RE disappeared for the ceramics with x = 0.01 and 0.02. The ceramic with x = 0.01 exhibited the highest remanent polarization (P-r = 37.2 mu C/cm(2)) and highest piezoelectric constant (d(33) = 137 pC/N). (C) 2016 Elsevier Ltd. All rights reserved.