Investigation of the structure and magnetic properties of Sn substituted Li-Zn ferrites fabricated by sol–gel process

A series of Sn doped Li-Zn ferrite powders with composition of Li_(0.2+0.5x)Zn_0.6Sn_xFe_(2.2−1.5x)O₄ (x = 0.00, 0.02, 0.04, 0.06, and 0.08) are synthesized by sol–gel process. The ring-shaped bulk samples of all compositions are obtained by sintering at 950 °C for 3 h, and all the structural and magnetic measurements were carried out on the sintered bulk samples. X-ray diffraction (XRD) patterns confirmed the formation of single-phase spinel structure when x ≤ 0.06 and the second phase of SnO₂ at x = 0.08. Field emission scanning electron micrograph (FE-SEM) is used to observe the surface morphology of the bulk samples and particle sizes (D_SEM). Micrograph of the sample for x = 0.08 shows many small particles appearing on the surface of the aggregation bulk samples. Vibrating sample magnetometer (VSM) is employed to study the saturation magnetization (M_s) and coercivity (H_c). The M_s displays a downtrend with the increasing of doping concentration and all samples have a lower coercivity of less than 30 Oe. Initial permeability (μ_i) and Curie temperature (T_c) are measured in a furnace using HP4294A impedance analyzer. The μ_i increases with the Sn⁴⁺ concentration until x = 0.06 and the T_c decreases with the Sn⁴⁺ concentration. The cation distribution estimated from XRD pattern and magnetic properties analyses suggest that Li⁺ ions appear in the tetrahedral sites with increasing of Sn⁴⁺ and Li⁺ contents.