Effect of fuel on the synthesis, structural, and magnetic properties of M-type hexagonal SrFe₁₂O₁₉ nanoparticles

Abstract

The aim of this work is to compare the formation temperatures, structural, and macroscopic magnetic properties of Sr-hexaferrite (SrM) in the presence of different fuels. In this research, SrM powder was synthesized by a sol–gel auto-combustion route using different hydroxycarboxylic acids: citric acid, tartaric acid, sucrose (gluconic acid), and lactic acid. Completion of reaction was followed by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The obtained powders were further characterized by thermal gravimetric analysis–differential thermal analysis (TGA–DTA), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). Their magnetic properties were studied using Mössbauer spectroscopy and magnetic measurements were done by vibrating sample magnetometer (VSM). The influence of different fuels was reflected on the formation temperature, phase purity, and morphology of crystallites as well as on their magnetic properties. The results show the finest crystallite size has been obtained as 27.85 nm (from XRD) in the case of sucrose sample. The lowest calcination temperature of 800 °C is obtained in the case of citric acid and tartaric acid samples, while sintering at 900 °C is necessary when sucrose was applied as a fuel. Lactic acid sample results in low phase purity even at 1000 °C. All the four samples show high level of magnetic properties. However, the sample prepared by citric acid as fuel has the highest specific saturation magnetization (M_S) and that with sucrose has the highest coercivity (H_C) while the sample prepared using lactic acid has the lowest magnetic parameters.