Enhanced thermal stability of lead-free high temperature 0.75BiFeO3-0.25BaTiO3 ceramics with excess Bi content

Lead-free high temperature 0.75BiFeO(3)-0.25BaTiO(3) (0.75BF-0.25BT) ceramics with different excess Bi contents were prepared by solid state reaction method. XRD results indicated that the modified 0.75BF-0.25BT ceramics exhibited single perovskite structure with pseudo-cubic symmetry. The room temperature piezoelectric constant d(33) a nd remnant polarization P-r were improved by the introduction of excess Bi content, while the temperature stability of dielectric and piezoelectric properties were enhanced. The 0.75BF-0.25BT ceramics with 1% excess Bi had a Curie temperature T-c of 508 degrees C, dielectric constant epsilon of 440, loss tan theta (1 kHz) of 4.6%, remnant polarization of 34.4 mu C/cm(2), piezoelectric constant d(33) of 114 pC/N, and planar electromechanical coupling factor k(p) of 0.31. The piezoelectric constant d(33), and planner electromechanical coupling factor k(p) of 0.75BF-0.25BT ceramics with 1% excess Bi were stable up to 450 degrees C, about 300 degrees C higher than that of PZT-based ceramics. The combination of improved piezoelectric constant d(33) and electrical temperature stability indicated that 0.75BF-0.25BT ceramics with proper concentration of excess Bi were promising candidates for high-temperature and lead-free piezoelectric applications. (C) 2013 Elsevier B. V. All rights reserved.