Effect of divalent cations (Co2+ and Ni2+) on microstructure, physical properties and application of Nd

Abstract

The nanocrystalline samples Nd1–xMxFeO3 (x = 0.0 and 0.1; M: Co2+ and Ni2+) were prepared using the citrate combustion method. The X-ray diffraction (XRD) pattern confirmed that the nanoparticles were synthesized in an orthorhombic structure. The particle size of Nd1–xMxFeO3 is in the range of 29–59 nm. The selected area electron diffraction (SAED) indicates the samples were prepared in a polycrystalline nature. The samples Nd1–xMxFeO3 (x = 0.0 and 0.1; M: Co2+ and Ni2+) have antiferromagnetic behavior. The Fe3+ spins are aligned antiparallel, forming the antiferromagnetic (AFM) properties, which are affected by many factors such as the bond angle between the Fe3+ (Fe3+–O2––Fe3+) and the Dzyaloshinskii-Moriya (D-M) interaction. The doping of Co2+ and Ni2+ ions in NdFeO3 enhances the magnetic properties of the NdFeO3. The saturation magnetization (Ms) of Nd0.90Co0.10FeO3 increases 1.8 times more than that of NdFeO3. The exchange bias field (HEX) of the Co-doped sample is two times greater than that of NdFeO3. The magnetic anisotropy constant (K) of the 10 % Co-doped sample increases by 11 factors compared to that of NdFeO3. The Tauc plot illustrates that the samples have a direct optical transition. The divalent cation substitution (Co2+ and Ni2+) decreases the optical band gap of NdFeO3, leading to the recommendation of using the samples Nd0.90Co0.10FeO3 and Nd0.90Ni0.10FeO3 in photocatalysis of dye degradation from water. The removal efficiencies of Cr6+ at pH = 6 are 88.06 %, 85.54 %, and 85.52 % for the samples NdFeO3, Nd0.90Co0.10FeO3, and Nd0.90Ni0.10FeO3, respectively. The Freundlich isotherm mode is the best-fit model for NdFeO3 to adsorb Cr6+ ions from aqueous solutions.