Achieving enhanced electrical properties and temperature stability in 0.6BiFeO3–0.4BaTiO3 lead-free piezoelectric textured ceramics

Abstract

As a promising lead-free and high-temperature piezoelectric material system, BiFeO3–BaTiO3 has drawn increasing research interest. The 0.6BiFeO3–0.4BaTiO3 textured ceramics have been synthesized using the templated grain growth method with BaTiO3 templates. Both the slurry for tape-casting and sintering conditions for green pellets were optimized in order to improve the ceramic quality and texture degree. The microstructure analysis indicates obvious template induced grain growth. A texturing degree with a Lotgering factor f of 75% is achieved. The volume expansion and the reduced phase transition temperatures were found in the ceramics after texturing, which suggests the chemical modification effects from dissolving templates. The textured sample shows a lower dielectric permittivity than the non-textured sample, implying the possible tetragonal rather than rhombohedral symmetry in the system. The textured ceramic exhibits superior ferroelectric properties due to the increased dielectric strength, with a remnant polarization of 12 μC/cm2 and a coercive field of 21 kV/cm under an applied field of 80 kV/cm. The reduced Ec with increasing temperature suggests the ferroelectric softening at elevated temperatures. The piezoelectric coefficient d33* reaches 222 pm/V at room temperature (RT). The variation in d33* with temperature from RT to 200 °C is only within +9.6% to −4.2% of d33* at RT, indicating significantly enhanced high-temperature stability. In addition, the strain hysteresis gradually decreases with increasing temperature, suggesting improved piezoelectric loss at high temperature. The results demonstrate a synergistic beneficial effect of texturing and chemical modification on the electrical properties of BiFeO3–BaTiO3 outside the morphotropic phase boundary, making it promising for high-temperature applications.