Effect of co-doping on structural, microstructural, dielectric, impedance and magnetic properties of sol-gel synthesized Bi_(1-x)Tr_xFe_(1-y)Mn_yO₃ (Tr = Cr, Ni, Zn, Cu) multiferroic nanoceramics

Nano-crystalline powders of Bi_(1-x)Tr_xFe_(1-y)Mn_yO₃ (where x & y = 0, 0.05 and Tr = Cr, Ni, Zn, Cu) were prepared using sol-gel autocombustion method. Structural studies on the calcined nanopowders using X-ray diffraction and Fourier transform infrared spectroscopy confirm the perovskite phase with rhombohedrally distorted structures. Microstructural studies using scanning electron microscopy and energy dispersive spectroscopy on the sintered surfaces display uniformly knitted fine grained microstructures with thin grain boundaries and the presence of all element’s constituent for the synthesis of the samples, respectively. Dielectric properties were evaluated at various frequencies and temperatures and found to follow space charge polarization with significantly reduced dielectric losses at all frequency ranges investigated. Impedance study on the samples aids in understanding the contributions of electrical conductivity and interfacial polarization, and the results verify the claims explained during the dielectric property investigation. Magnetic studies on the samples reveal that among all the samples, Cr/Mn co-doped (BCrFMO) sample shows significant enhancement in the value of saturation magnetization (3.718 emu/g) while Ni/Mn co-doped (BNiFMO) sample demonstrates higher coercivity (259.734 Oe) at room temperature. With all enhanced structural, microstructural, dielectric and magnetic order through the influence of co-doing, these materials are highly recommended for spintronic, multifunctional memories, sensors, and actuators.