Enhanced high-temperature piezoelectric properties of Bi(Zn_0.5Ti_0.5)O₃-modified BiFeO₃–BaTiO₃ ceramics

This paper reports enhanced high-temperature piezoelectric properties of Bi(Zn_0.5Ti_0.5)O₃-modified BiFeO₃-BaTiO₃ (BF–BT-xBZT) ceramics prepared by two-step sintering method. The resultant ceramics show a symmetrical transition from a rhombohedral–pseudo-cubic (R-PC) phase coexistence to main PC phase with the increase of x, whose R-PC fraction (C_R/C_PC) is 53.3/46.7, 52.9/47.1, 50.2/49.8, 27.4/72.6, 15.3/84.7 when x = 0, 0.005, 0.01, 0.03, 0.05, respectively. The modification of BZT inhibits the grain growth, reduces the leakage current and gradually drives ferroelectric to relaxor transition. Optimal piezoelectric properties: d ₃₃ = 193 pC N⁻¹, P _r = 20.6 μC cm⁻², T _C = 503 °C and k _p = 36% achieved at x = 0.01 composition, which is due to the synergistic effect of an appropriate C_R/C_PC ratio, improved insulation and good polarization performance. In addition, the depolarization temperature T _d is close 280–312 °C, and the high-temperature d ₃₃ further increases to 286–347 pC N⁻¹, which shows a good application prospect of lead-free piezoceramics at high temperature. Our work also confirms that the addition of (Zn_0.5Ti_0.5)³⁺ and two-step sintering method are an effective and convenient strategy to improve the high-temperature electrical performance of BiFeO₃–BaTiO₃ based lead-free ceramics.