Figure 5. Ferroelectric properties of the Bi_4.2K_0.8Fe₂O_9+δ nanobelts.

(a) P–E and J–E loops of the bulks made of the Bi_4.2K_0.8Fe₂O_9+δ nanobelts at 300 K. (b) Temperature dependence of electric polarization in zero (blue line) and 50 kOe (red line) magnetic fields, and the value of the polarization was acquired by integrating the pyroelectric current. For the measurements the nanobelts were pressed into a bulk with a cuboid shape (2 × 2 × 0.5 mm³) under a pressure of 20 MPa at room temperature. (c) Temperature dependent c/a measurements for the Bi_4.2K_0.8Fe₂O_9+δ nanobelts, the yellow wide line is guide to eyes.