Largely enhanced electromechanical properties of BaTiO3-(Na0.5Er0.5)TiO3 lead-free piezoelectric ceramics

Abstract

Lead-free (1 − x)BaTiO3-x(Na0.5Er0.5)TiO3 (0 ≤ x ≤ 0.15) ceramics were prepared by a solid state reaction method. Their structure and electric properties were analyzed. Rietveld refinements suggested that the ceramics crystallized in the tetragonal perovskite space group P4 mm at room temperature. With increasing x from 0 to 0.05, Na+/Er3+ co-substitution at Ba-site in BaTiO3 leads to the decrease of lattice parameters and unit cell volume. While minor secondary phase, Er2Ti2O7 and (TiO1.2)0.787, appears at x = 0.10 or above. A great enhancement of piezoelectric properties and other electric parameters was obtained in this system by properly moderating the compositions. For example, in the ceramics with composition x = 0.05, a large piezoelectric coefficient d33 (333 pm/V), a high remnant polarization Pr (14.3 μC/cm2), a good planar electromechanical coupling factor kp (0.391), a mechanical quality factor Qm (97.3), and a high Curie temperature (TC = 134 °C) (higher than that of pure BaTiO3) were achieved. Our results show that (1 − x)BaTiO3-x(Na0.5Er0.5)TiO3 ceramics are a good candidate of lead-free piezoelectric materials.