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Keywords:

  • Bi0.5Na0.5TiO3;
  • ferroelectric properties;
  • lead-free ceramics;
  • piezoelectric properties

Abstract

Lead-free (Bi0.5Na0.5)1–xyz(Bi0.5K0.5)xBay(Bi0.5Li0.5)zTiO3 piezoelectric ceramics have been prepared by a conventional ceramic technique and their structure and electrical properties have been studied. The results of XRD diffraction show that after the addition of K+, Ba2+, and Li+, a new Bi0.5Na0.5TiO3-based solid solution with a pure perovskite structure is obtained and a morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases is formed at 0.10 < x < 0.20, 0.01 < y < 0.04, and z = 0.075. The partial substitutions of (Bi0.5K0.5)2+, Ba2+, and (Bi0.5Li0.5)2+ for the A-site (Bi0.5Na0.5)2+ ions of Bi0.5Na0.5TiO3 decrease effectively the coercive field Ec and improve significantly the remanent polarization Pr. The piezoelectricity of the ceramics is greatly enhanced because of the MPB, lower Ec and higher Pr. The ceramic with x = 0.15, y = 0.02, and z = 0.075 situated at the MPB exhibits the optimum piezoelectric properties, giving d33 = 209 pC/N and kp = 30.5%. Two dielectric anomalies are observed, suggesting diffuse phase transition characteristics. The depolarization temperature Td reaches a minimum value near the MPB. The deformed PE loop is observed near/above Td, indicating that the ceramics may contain both the polar and nonpolar regions.