Spinel ferrite nanocomposites of Ni_1–xZn_xFe₂O₄ (x=0.25 and 0.75) were synthesized by sol-gel auto-combustion and annealed between 250°C and 1000°C. A single-phase spinel structure was found through X-ray diffraction (XRD). The crystallite size is in the range of 17.5566.98nm, and lattice parameters are in the range of 8.3518.434Å. X-ray analysis revealed a slight shift of the peaks towards shorter angles when the zinc concentration increased from 0.25 to 0.75. XRD measurements revealed the metal ion distribution in the spinel ferrite system. For each sample, XRD data were used to compute structural characteristics such as lattice spacing, lattice constant, crystallite size, oxygen position parameter, tetrahedral and octahedral ionic radii, and bond lengths. Energy dispersive spectroscopy (EDS) spectra and field emission-electron scanning microscope (FESEM) were used to evaluate the elemental content and morphology. EDS analysis confirmed the presence of expected elements in the samples and confirmed the high doping rate of more than 180 of Zn ions in Ni ferrite. The evaluated particle sizes were determined to be 79.2 and 118.4nm for zinc content of 0.25 and 0.75, respectively. The nearly spherical shape of the nanoparticles was shown in the transmission electron microscope (TEM). The magnetic moment, remanent, coercivity, and saturation magnetization were calculated by using vibrating sample magnetometer (VSM) results. The saturation magnetization magnitudes showed the influence of cation distribution.

In this study, strontium hexaferrite nanoparticles synthesized by sol–gel autocombustion method and the effect of high annealing temperature on produced nanoparticle have been studied. Powders were annealed at 1,000 and 1,300°C. Structural properties of synthesized powders were analyzed by X‐ray diffraction (XRD). Hexagonal structure and shape of SrFe₁₂O₁₉ nanoparticles were analyzed from field‐emission scanning electron microscope and transmission electron microscope figures. Fourier‐transform infrared spectroscopy confirmed the formation of an M‐type hexagonal structure. The thermal behavior of nanoparticles has been investigated by thermogravimetric analysis (TGA and DTG). Height measurement of nanoparticles with 2D and 3D images of the surface obtained from atomic force microscopy. XRD pattern of strontium hexaferrite nanoparticle was used for determining the crystal structure and examining the effect of high annealing temperature on powders by finding lattice parameters, densities, crystallite size, specific surface area, and strain. Crystallite size, strain, and bulk density decreased when produced nanoparticles annealed at 1,000°C with decreased porosity when nanoparticles were annealed at 1,300°C. The specific surface area was found to be increased when nanoparticles were annealed at 1,000°C. In this study, influence of high temperature on the structure of SrFe₁₂O₁₉ nanoparticles was studied.

The structural, magnetic, and dielectric properties of a series of Ni²⁺ substituted cobalt nanoferrite particle samples with the composition Co_1−xNi_xFe₂O₄ (where x = 0.0 ≤ x ≤ 1.0) synthesized by using the sol-gel auto combustion route are presented in this report. The electromagnetic interference shielding of Co_1−xNi_xFe₂O₄/PVA nanocomposite films has been determined in the microwave X-band (8.2–12.4 GHz) frequencies. X-ray analysis revealed the single-phase formation of nickel-substituted cobalt nanoferrite samples. The decreasing trend of lattice parameters with Ni²⁺ substitution indicates the incorporation of Ni²⁺ into the crystal structure, obeying Vegard’s law. FTIR showed the absorption bands at 560–590 cm⁻¹ () and 390–400 cm⁻¹ () were attributed to (A-site) tetrahedral and (B-site) octahedral groups complex, respectively which confirm the spinel structure of the samples. Field emission scanning electron microscopy showed agglomerated grains of different sizes and shapes in the morphological observation. EDS reveals the chemical composition of the prepared samples. TEM analysis revealed that the synthesized particles were nearly monodisperse, show to be roughly spherical in shape, and have a polycrystalline nature. The dielectric constant and loss tangent (tanδ) is found to decrease with increasing frequency which shows normal behavior for ferrimagnetic materials. The magnetic properties determined using VSM have substantially changed with the substitution of Ni²⁺ ions. The saturation magnetization and the experimentally magnetic moment are observed to decrease with an increase in Ni²⁺ content x. A series of Co_1−xNi_xFe₂O₄/PVA nanocomposite films are prepared by applying simple, rapid, and inexpensive methods for EMI shielding materials. The vector network analyzer data were used to evaluate the electromagnetic interference (EMI) shielding properties of the Co_1−xNi_xFe₂O₄/PVA samples. At 9.2 GHz, a study of reflection loss showed a minimum reflection loss (RL) of −32.08 dB. Also, the synthesized Co_1−xNi_xFe₂O₄/PVA nanocomposite samples show improved performance for EMI efficiency which proves the utility of this doping. With this low RL value, the results and techniques also promise a simple, effective approach to achieve light-weight Co_1−xNi_xFe₂O₄/PVA nanocomposite films and make it excellent microwave absorbers, capable of working at gigahertz frequencies for application potentials in EMI shielding material, communication, radar stealth technology, and electronic warfare.