Giant Polarization and High Temperature Monoclinic Phase in a Lead-Free Perovskite of Bi(Zn_0.5Ti_0.5)O₃‑BiFeO₃

Lead-free piezoelectrics have attracted increasing attention because of the awareness of lead toxicity to the environment. Here, a new bismuth-based lead-free perovskite, (1 – x)­Bi­(Zn_0.5Ti_0.5)­O₃-xBiFeO₃, has been synthesized via a high-pressure and high-temperature method. It exhibits interesting properties of giant polarization, morphotropic phase boundary (MPB), and monoclinic phase. In particular, large tetragonality (c/a = 1.228) and giant spontaneous polarization of 110 μC/cm² has been obtained in 0.6 Bi­(Zn_0.5Ti_0.5)­O₃-0.4BiFeO₃, which is much higher than most available lead-free materials and conventional Pb­(Zr,Ti)­O₃. MPB is clearly identified to be constituted of tetragonal and monoclinic phases at x = 0.5. Notably, a single monoclinic phase has been observed at x = 0.6, which exhibits an intriguing high-temperature property. The present results are helpful to explore new lead-free MPB systems in bismuth-based compounds.