Effect of La substitution on the struture and multiferroic properties of BiFeO3-PbTiO3 crystalline solutions

Crystalline Solutions of 0.6(Bi_1-xLa_x)FeO₃-0.4PbTiO₃ (BLF-PT) for x = 0, 0.1 and 0.2 have been synthesized by the solid-state reaction method. X-ray diffraction results reveal that BLF-PT of x = 0 has the strong tetragonal distortion with the c/a ratio of about 1.17. However, the La substitution modifies BLF-PT into the rhombohedral structure. The dielectric loss at low frequency (10² ~ 10⁴ Hz) is significantly reduced by addition of La. Moreover, the giant remnant polarization of 64.8 muC/cm² is achieved for BLF-PT of x = 0.2. The weak ferromagnetic phenomenon in BLF-PT is observed with the increase of La concentration. X-ray photoelectron spectroscopy (XPS) investigation shows that the valent variation of Fe³⁺rarrFe²⁺ could be effectively suppressed by La substitution.