Giant Polarization and High Temperature Monoclinic Phase in a Lead-Free Perovskite of Bi(Zn<sub>0.5</sub>Ti<sub>0.5</sub>)O<sub>3</sub>‑BiFeO<sub>3</sub>

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 – <i>x</i>)­Bi­(Zn<sub>0.5</sub>Ti<sub>0.5</sub>)­O<sub>3</sub>-<i>x</i>BiFeO<sub>3</sub>, 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 (<i>c</i>/<i>a</i> = 1.228) and giant spontaneous polarization of 110 μC/cm<sup>2</sup> has been obtained in 0.6 Bi­(Zn<sub>0.5</sub>Ti<sub>0.5</sub>)­O<sub>3</sub>-0.4BiFeO<sub>3</sub>, which is much higher than most available lead-free materials and conventional Pb­(Zr,Ti)­O<sub>3</sub>. MPB is clearly identified to be constituted of tetragonal and monoclinic phases at <i>x</i> = 0.5. Notably, a single monoclinic phase has been observed at <i>x</i> = 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.