Praseodymium doped Ni-Co based spinel ferrite nanoparticles prepared for energy storage applications

Praseodymium doped nickel-cobalt based spinel ferrite (Ni_0.5Co_0.5Pr_xFe_2-xO₄) nanoparticles with doping concentration (x = 0.00 to 0.20) were synthesized via using sol-gel and annealed at 600 °C. The X-ray diffraction (XRD) technique revealed the existence of the of FCC spinel phase of nanoparticles. The crystallite size was determined using Scherrer's formula and found within the range of 9–17 nm. Transmission electron microscopy (TEM) has confirmed the existence of non-uniform grain enlargement characterized by agglomeration, non-homogeneity in size and shape nanoparticles. Fourier transform infrared spectroscopy (FTIR) confirms the formation of a spinel structure through the detection of characteristic vibrational bands around 400 and 600 cm⁻¹, corresponding to the octahedral and tetrahedral sites, respectively. An impedance analyzer was employed to investigate dielectric parameters across a frequency range from 1 MHz to 3 GHz. The observed peaks at high frequency are called as relaxation peaks which are due to the electron hopping between multilayer grains. The magnetic properties of the nanoparticles have been studied by using vibrating sample magnetometer (VSM). Hysteresis loop has revealed that the nanoparticles have soft magnetic behavior. The parameters such as saturation magnetization (M_s), remanent magnetization (M_r), squareness (M_r/M_s) and magnetic moment (μB) of the nanoparticles have decreased and coercivity (H_c) has increased with the substitution Pr³⁺ ions. The observed change in the dielectric properties suggest that the prepared nanoparticles can be used for as energy storage devices at high frequency.