Hydrothermal synthesis and structure evolution of metal-doped magnesium ferrite from saprolite laterite

Abstract

Spinel metal-doped magnesium ferrite (MgFe₂O₄) was synthesized using an atmospheric hydrochloric acid leaching process and hydrothermal synthesis process from saprolite laterite. The effects of the hydrothermal preparation conditions, such as pH value of the acid leaching solution, hydrothermal temperature and time, on the formation of magnesium ferrite were systematically investigated. It was shown that pure magnesium ferrite could be obtained when the pH value of the leaching solution was controlled at 12.0 and the hydrothermal reaction was conducted at 160 °C for 6 h. More importantly, the structural evolution of the as-prepared magnesium ferrite was investigated in detail using X-ray diffraction (XRD), X-ray fluorescence (XRF), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM). The results indicated that the metal-doped magnesium ferrite displayed soft ferrimagnetic behavior and the magnesium ions migrated from the tetrahedral site to the octahedral site as the calcination temperature increased. The formed magnesium ferrite was indeed mixed with traces of other magnesium-containing compounds.