Abstract
Powders of calcium-substituted hematite were synthesized via hydrothermal method. The samples were characterized using X-ray diffraction, Mössbauer spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and magnetometry. Structural analysis revealed that Ca-substituted samples maintained single-phase hematite for Fe/Ca ratios between 11 and 5. Further increase in calcium concentration led to formation of a defective iron-calcium spinel phase. Infrared spectra confirmed the presence of hydroxyl groups within the hematite lattice. The incorporation of calcium and associated defects significantly influenced the magnetic properties of hematite, inducing ferromagnetic behavior. The maximum magnetization value of 12.9 emu/g was achieved at Fe/Ca = 6, representing a substantial enhancement compared to most other doped hematites. These materials show potential for applications in hyperthermia, MRI contrast enhancement, and wastewater treatment.