High temperature dielectric, ferroelectric and piezoelectric properties of Mn-modified BiFeO₃-BaTiO₃ lead-free ceramics

Lead-free and high-temperature 0.71BiFeO₃-0.29BaTiO₃ ceramics with Mn modification (BF-BT-x %Mn) were fabricated by conventional solid-state reaction method, and the high temperature dielectric, ferroelectric and piezoelectric properties were investigated. All compositions exhibited pseudo-cubic phases. Mn modification improved the electrical properties of BF-BT solid solutions at both room and high temperature. The Curie temperature T _C, depolarization temperature T _d, dielectric constant ε _r, dielectric loss tanδ, piezoelectric constant d ₃₃, electromechanical coupling factor k _p, remnant polarization P _r of BF-BT-1.2 %Mn ceramics were 506, 500 °C, 556, 0.04, 169 pC N⁻¹, 0.373, 31.4 μC cm⁻², respectively. The ε _r, tanδ, and k _p of BF-BT-1.2 %Mn ceramics were stable with the increase of temperature until 500 °C. The coercive field E _c of BF-BT-1.2 %Mn ceramics was nearly 30 kV cm⁻¹ at 200 °C, which was much larger than those of PZT, BS-PT,BNT and KNN ceramics. The high field strain coefficient d*₃₃ reached as large as 525 pm V⁻¹ at 200 °C. These results showed that the BF-BT-x %Mn ceramics were promising candidate for high temperature piezoelectric applications.