High-performance BiFeO3BaTiO3 lead-free piezoceramics insensitive to off-stoichiometry and processing temperature

It is well-known that the performance of BiFeO3BaTiO3 (BF-BT) ceramics is sensitive to composition, calcining and sintering temperature (Tcal and Tsint) due to the formation of Bi25FeO39 and/or Bi2Fe4O9 impurities and/or the volatilization of Bi2O3. We report remarkably stable electrical properties over the range of −0.03 ≤ x ≤ 0.05 and 930 °C ≤ Tsint ≤ 970 °C in 0.7Bi(1+x)FeO3-0.3BaTiO3 ceramics prepared by one-step process. This method avoids the thermodynamically unstable region of BiFeO3 and prevents the formation of Bi25FeO39 and/or Bi2Fe4O9 impurities even when the addition of α-Bi2O3 raw material is intentionally deficient or rich to make off-stoichiometric BF-BT, thus greatly improving the robustness of compositional and processing. Rhombohedral-pseudocubic phase coexists in all ceramics, and their CR/CPC fraction are 48.0/52.0–50.6/49.4 and 55.9/44.1–56.6/43.4 when x increases from −0.05 ≤ x ≤ 0 to 0.01 ≤ x ≤ 0.05. The stable electrical properties of d33 = 180–205 pC/N, Pr = 17.9–23.8 μC/cm2, and TC = 485–518 °C are achieved. The maximum d33T/d33RT of BF-BT is twice that of soft PZT, superior to most the-state-of-art lead-free ceramics. Our results provide a synthesis strategy for designing high performance piezoelectric materials with good stability and easy industrialization.