Ce3+ doped Nickel Zinc ferrites have been synthesised by sol-gel method followed by sintering at 4000C for 4 hours. Powder X-ray diffraction patterns of the prepared samples confirm the formation of single phase cubic spinel structure. Crystallite size of samples doped with Ce are smaller than that of undoped ferrite. The lattice parameters decrease with increase in doping concentration of Ce3+ ion. W-H plots are drawn to study the strain effect in crystal structure.SEM micrographs show formation of spherical shaped nanoparticles. The vibration bands corresponding to metal oxygen vibrations at tetrahedral and octahedral sites in the FTIR spectra are in the reported range suggesting Ce3+occupation on octahedral sites predominantly. The doped samples exhibited lower saturation magnetization. The relative permittivity is found to show a decreasing trend with increase in frequency for all the samples which is characteristic of normal ferrimagnetism. The AC conductivity initially increases with frequency then remains constant over a wide range of frequencies. The UV analyses give the band gap which is less than 2 eV for all the samples which show that these are semiconducting materials.
Rare earth doped spinel ferrites belonging to the series Ni 0.6 Zn 0.2 Me 0.2 Gd x Fe 2-x O 4 (where Me= Mg/Mn, x=0/0.06) were synthesized by sol-gel method. The characterizations of the prepared samples were performed using X-rayDiffraction (XRD), High Resolution Transmission Electron (HRTEM) Microscopy, Vibrating Sample Magnetometry (VSM), X-ray Photoelectron Spectroscopy (XPS) and Open aperture z-scan technique. The XRD patterns confirm the crystallization of the ferrites in cubic form with spinel structure. The average crystallite size calculated using Debye-Scherrer's equation is in 10-20 nm range. The HRTEM images reveal the formation of spherically shaped agglomerated nanoparticles. The magnetic parameters such as remanence magnetization (M r ), coercivity (H c ) and saturation magnetization (M s ) were obtained from the hysteresis curves. The samples show better optical limiting parameters than reported which make them promising materials for non-linear applications requiring low limiting thresholds. Owing to their low band gaps ferrites can be efficiently used for the photo catalysis of organic dyes with visible solar energy which constitutes a major portion of sunlight. Ferrites have an added advantage by virtue of their spinel lattice which makes available extra catalytic sites. In the present work, the photocatalytic activity under visible sunlight irradiation was explored from the degradation of Methylene Blue (MB) and Rhodamine B (RhB) dyes. Higher photocatalytic efficiency was exhibited by magnesium containing samples. Near total decolouration of dye solution subjected to magnetic separation has not been reported before. The improvement in photocatalytic degradation efficiency is due to the adsorption followed by effective separation and prevention of photo generated electron-hole pair recombination for a longer period by these ferrites. To further aid the degradation, H 2 O 2 was added as precursor to the reactive mixture which increases the formation of hydroxyl radical (OH · ).
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