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

Lead-free high temperature 0.75BiFeO3-0.25BaTiO3 (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 d33 and remnant polarization Pr 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 Tc of 508 °C, dielectric constant ɛ of 440, loss tan θ (1 kHz) of 4.6%, remnant polarization of 34.4 μC/cm2, piezoelectric constant d33 of 114 pC/N, and planar electromechanical coupling factor kp of 0.31. The piezoelectric constant d33, and planner electromechanical coupling factor kp of 0.75BF-0.25BT ceramics with 1% excess Bi were stable up to 450 °C, about 300 °C higher than that of PZT-based ceramics. The combination of improved piezoelectric constant d33 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.