Large ferroelectric polarization of chemical solution processed BiFeO3–PbTiO3 thin films

• Polycrystalline films of BF–xPT with x=0.25–0.35 prepared by solution deposition.
• Crystal structure at x=0.25 is monoclinic (Cm) rather than rhombohedral as in bulk.
• At x=0.30 and x=0.35, monoclinic (Cm) phase coexists with tetragonal (P4mm) phase.
• All samples show saturated hysteresis loops at RT with 2 Pr∼160 μC/cm2 at x=0.25.
• High polarization is attributed to high polarizability of monoclinic phase present.

We report unusually high ferroelectric polarization in chemical solution processed thin films of BiFeO3–PbTiO3 (BF–xPT) of compositions near the morphotropic phase boundary (MPB). Saturated hysteresis loops were obtained showing a large remnant polarization of 80 μC/cm2 in thin films of composition BF–0.25PT with polarization decreasing for BF–0.30PT and BF–0.35PT. Structural analysis revealed single phase region with monoclinic Cm space group for composition x=0.25 while a two phase region of monoclinic (Cm) and tetragonal (P4mm) phase exists at x=0.30–0.35. The large polarization in BF–0.25PT films is attributed to superior polarizability of the monoclinic Cm phase.