Figure 4. Electric polarization and phase transition of KBiFe₂O₅.

(a) Dielectric constant of KBiFe₂O₅ as a function of temperature measured at 10^1–4 Hz, using amplitude of 1 V. (b) Corresponding dielectric loss tangent as a function of temperature. (c) Polarized optical images of KBiFe₂O₅ single crystal from room temperature to 773 K showing polarizing light decreasing with temperature and disappearing at 773 K. The transition temperature of 773 K roughly coincides with the cell-doubling transition at 773 K determined by XRD. (d) Topography image (top left) and the corresponding PFM image (top right) along with local piezoelectric response hysteresis loop (bottom) of KBiFe₂O₅ single crystal. (e) P-E hysteresis loops measured at room temperature at increasing scan field ranges.