Effect of pH and Calcination Temperature on the Structural, Optical, Electrical, and Magnetic Properties of Co-Precipitated Iron Oxide Nanomaterials
DOI:
https://doi.org/10.48048/tis.2026.12091Keywords:
Iron oxide, Co-precipitation, Optical property, Energy band gap, Electrical resistance, Electrical conductivity, Magnetic properties, Coercivity, RemanenceAbstract
Iron oxide nanomaterials were synthesized by co-precipitation, with pH adjusted from 9 to 12, and subsequent calcination carried out between 300 and 900 °C. The as-synthesized samples were characterized for morphology, crystal structure, and functional properties. At pH 11, nearly spherical nanoparticles with uniform size and high crystallinity were obtained, giving the highest saturation magnetization of 121.97 emu/g and a narrow indirect optical band gap of 2.03 eV, beneficial for magnetic hyperthermia and visible-light photocatalysis. Calcination at 500 °C retained the γ-Fe2O3 phase and yielded peak electrical conductivity (98.62×10−9 (Ω·cm)−1) together with near-superparamagnetic behavior with low coercivity and remanence, making it suitable for spintronics and biomedical applications. In contrast, annealing above 500 °C triggered irreversible conversion to antiferromagnetic α-Fe2O3, which sharply reduced magnetization and increased electrical resistivity. Combined structural, optical, and magnetic data indicate that pH 11 with 500 °C provides the most favorable trade-off between defect density, phase stability, and interparticle connectivity. Therefore, this work demonstrates that the dual-parameter control of pH and calcination temperature allows the optimization of structural, optical, electrical, and magnetic properties, enabling the development of multifunctional iron oxide nanomaterials for catalysis, biomedicine, and next-generation electronic devices.
HIGHLIGHTS
- Iron oxide nanomaterials were synthesized by co-precipitation and tuned by varying pH (9 - 12) and calcination temperature (300 - 900 °C).
- pH 11 produced uniform spherical nanoparticles with reduced spin disorder, yielding the highest magnetization (121.97 emu/g).
- Calcination at 500 °C was identified as the “optimum temperature,” maximizing electrical conductivity and near-superparamagnetic behavior.
- Higher calcination temperatures (> 700 °C) triggered a phase transition from maghemite to hematite, causing loss of magnetism and higher resistivity.
- Optical band gap tuning was achieved: Stable 2.03 eV at pH 9 - 11 and widened to 2.12 eV at pH 12 due to reduced defect states.
- Dual optimization (pH 11 and 500 °C) provides a simple experimental strategy for multifunctional nanomaterials in spintronics, catalysis, and biomedicine.
GRAPHICAL ABSTRACT
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