Structural, morphological, optical, and magnetic properties of rare earth Bi3+ doped Ni–Co ferrites via the citate-gel auto combustion method and applications

Abstract

Sol-gel combustion was used to create a series of bismuth-doped nickel cobalt nanoferrites with the chemical composition Ni_0.8Co_0.2Fe_2-xBi_xO₄ (x = 0.00, 0.02, 0.04, and 0.06) (NCFB), which were then calcined at 500 °C. The single phase fcc crystal was verified by the X-ray diffraction (XRD) examination. From the samples to investigated Fourier Transform Infrared (FT-IR) spectra, Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (FE-SEM), and X-ray diffraction (XRD) in the structural and morphological investigations. The vibration sample magnetometer was used to determine the magnetic characteristics (VSM). Using the Debye-Scherrer equation, the crystallite sizes of each mixture were determined to be between 72 and 95 nm. It was discovered that as Bi³⁺ ion doping rose, correspondingly increased the lattice parameters. The SEM was used to examine the surface morphology, and TEM was used to establish the particle size. Two prominent absorption peaks were found in the frequency range of 500–4000 cm⁻¹ in the FT-IR investigations. The lower frequency band is located at 592 cm⁻¹, whereas the higher frequency band is located at 3741 cm⁻¹. It is evident that when the quantity of Bi³⁺ ions increased, the significant absorption bands seen in Figure 4 were somewhat moved towards the higher frequency side. Hysteresis is observed in VSM analysis when the synthesised samples are heated to 300 K. The findings showed that all Ni–Co nanoferrites doped with Bi³⁺ at 300 K had ferromagnetic character. For x = 0.000 (58.54 emu/g), 0.02 (58.96 emu/g), 0.04 (60.44 emu/g), and 0.06 (61.06 emu/g), saturated magnetisation was detected at 300 K. At 300K, the range of Hc values is 262.41 Oe to 350.52 Oe. The Remnant magnetisation value varied between 9.53 and 14.52 at 300 K.