Structural, physical, and magnetic properties of nanocrystalline manganese-substituted lithium ferrite synthesized by so
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Structural, physical, and magnetic properties of nanocrystalline manganese‑substituted lithium ferrite synthesized by sol–gel autocombustion technique W. R. Agami1 · M. A. Ashmawy2 Received: 13 April 2020 / Accepted: 18 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Nanoparticles of spinel ferrite L i0.5–0.5xMnxFe2.5–0.5xO4 (x = 0, 0.25, 0.5, 0.75 and 1) were prepared by sol–gel autocombustion technique. The crystalline phase formation, morphology, cation distribution, and magnetic properties of Li0.5–0.5xMnxFe2.5–0.5xO4 nanoferrite samples were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared (IR) spectroscopy, and vibrating sample magnetometer (VSM). The lattice parameter increases by Mn substitution, while both the crystallite size and Curie temperature (TC) decrease. Values for both the saturation magnetization (Ms) and the coercivity (Hc) were enhanced because both are larger for Mn-substituted samples than those for unsubstituted ones. The addition of Mn2+ ions promotes (Ms) until (x = 0.5) then an appreciable decrease occurs, whereas the coercivity (Hc) increases up to x = 0.25 then it decreases. The role of the substitution with M n2+ ions in changing all investigated properties of lithium ferrite was explained according to different theories. Keywords Li–Mn nanoferrite · Sol–gel autocombustion · IR spectroscopy · XRD · Magnetic properties
1 Introduction Lithium ferrite and substituted lithium ferrites have important and interesting technological applications, such as cathode materials in lithium-ion batteries [1–3]. They are commonly used in microwave applications and cores of high frequency inductors. The reason is that they have high (TC), good thermal stability, excellent hysteresis squareness, and economical price [4, 5]. In the past, the solid-state reaction method was used to produce these materials. This method has many disadvantages, like chemical inhomogeneity, coarser crystallite size, and introduction of impurities during ball milling [6–8]. Recently, co-precipitation, hydrothermal, and sol–gel preparation techniques have been developed [9–12]. More attention has been focused toward the citrate–nitrate precursor autocombustion method * W. R. Agami [email protected] 1
Physics Department, Faculty of Science, Ain Shams University, 11566 Abbassia, Cairo, Egypt
Basic Science Department, Modern Academy for Engineering and Technology, El Mokatam, Cairo, Egypt
2
which permits preparing ultra-fine powders with chemically homogeneous composition, uniform size, and good reactivity [13, 14]. In fact, some authors investigated Mn-substituted lithium ferrite with composition (Li0.5MnxFe2.5–xO4) (where Mn enters the chemical formula on the expense of Fe only) [15–21]. The effect of sintering temperature (1080, 1032, and 984 °C) on the structural, electrical, and magnetic properties of autocombustion prepared sample of composition Li0.45Mn0.1Fe2.45O4 was carried out [22]. The structural and dielectri
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