La3+ doped LiCo0.25Zn0.25Fe2O4 spinel ferrite nanocrystals: Insights on structural, optical and magnetic properties

• Published in: Journal of rare earths 2021-01, Vol.39 (1), p.75-82
• Main Authors: Abdel Maksoud, M.I.A., El-Ghandour, Ahmed, Ashour, A.H., Atta, M.M., Abdelhaleem, Soraya, El-Hanbaly, Ahmed H., Fahim, Ramy Amer, Kassem, Said M., Shalaby, M.S., Awed, A.S.
• Format: Article
• Language: English
• Subjects: Li-Co-Zn ferrite; Magnetic behavior; Optical properties; Rare earths; Superparamagnetic nature; Transformers core
• ISSN: 1002-0721; 2509-4963
• DOI: 10.1016/j.jre.2019.12.017

This paper addresses the manipulation of structural, morphology, optical and magnetic properties of LiCo0.25Zn0.25Fe2O4 ferrite via incorporation of different proportions of La3+ at the expense of iron ions using a sol-gel method. The samples were characterized using the X-ray diffraction technique (XRD), Fourier transform infrared (FT-IR) spectroscopy, the energy dispersive X-ray spectra (EDX), inductively coupled plasma optical emission spectroscopy (ICP-OES), high resolution scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, ultraviolet-diffuse reflectance spectroscopy (UV-DRS), and vibrating sample magnetometer (VSM) technique. The Rietveld refinements of the samples indicate that at higher concentrations of La3+, nanostructures with dual phase, i.e. cubic spinel and orthorhombic LaFeO3 perovskite with space group (Pbnm) appear. Optical studies show that the energy band gap (Eg) of the bare LiCo0.25Zn0.25Fe2O4 ferrite sample (2.18 eV) reaches up to 2.47 eV at x = 0.06 and above this concentration, it drops sharply to 2.00 eV. Although the saturation magnetization and the coercivity of LiCo0.25Zn0.25LaxFe2–xO4 are lower than that of LiCo0.25Zn0.25Fe2O4 NPs. Overall, the superparamagnetic nature and low values of saturation magnetization and coercivity of LiCo0.25Zn0.25LaxFe2-xO4 NPs are suitable to be applied in transformers core. The structural, optical, and magnetic properties of La3+ doped LiZn0.25Co0.25Fe2O4 nanocrystal were studied. With further increasing x more and more La3+ will accumulate at the grain boundaries and form a secondary phase of LaFeO3. It is evident from mapping images that the elements Zn, Co, Fe, La, S and O exist, further, those elements are homogeneously distributed. We found that the doped samples exhibit narrow band gaps (2.18–2.47 eV) as well as high porosity and surface area. Overall, the superparamagnetic nature and low values of saturation magnetization and coercivity (130.740–110.630 G) of La3+ doped LiZn0.25Co0.25Fe2O4 samples are suitable to be applied in transformers core. [Display omitted] •La3+ substituted Li-Co-Zn ferrite were successfully synthesized via facile sol-gel methodology.•Narrow band gap and the high porosity of LiCo0.25Zn0.25LaxFe2–xO4 are suitable to be applied in the catalysis applications.•Low coercivity values of LiCo0.25Zn0.25LaxFe2–xO4 reveal their potential for transformers core applications.