Enhanced Multiferroic Properties of YFeO₃ by Doping with Bi³

Tthe present work studied the cationic substitution of Y³⁺ by Bi³⁺ on the crystal structure of orthorhombic YFeO₃ and its effect over magnetic, dielectric and electric properties of multiferroic yttrium orthoferrite. Stoichiometric mixtures of Y₂O₃, Fe₂O₃ and Bi₂O₃ were mixed and milled for 5 h using a ball to powder weight ratio of 10:1 by high-energy ball milling. The obtained powders were pressed at 1500 MPa and sintered at 700 °C for 2 h. The test samples were characterized at room temperature by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and impedance spectroscopy (IS). The X-ray diffraction patterns disclosed a maximum solubility of 30 % mol. of Bi³⁺ into the orthorhombic YFeO₃. For higher concentrations, a transformation from orthorhombic to garnet structure was produced, obtaining partially Y₃Fe₅O₁₂ phase. The substitution of Bi³⁺ in Y³⁺ sites promoted a distortion into the orthorhombic structure and modified Fe-O-Fe angles and octahedral tilt. In addition, it promoted a ferromagnetic (FM) order, which was attributed to both the crystal distortion and Dzyaloshinskii-Moriya interaction. For doped samples, an increase in real permittivity values was observed, and reduced with the increase of frequency. This in good agreement with the Maxwell-Wagner effect.