Two Prussian blue (PB) samples with different morphologies (spheres, mean size 160 nm; cubes, mean size 1.48 μm) and variable content of potassium (K-free and K-bearing) were used as a precursor material for the preparation of iron(III) oxides by solid state thermal decomposition method. A mixture of iron(III) oxide polymorphs (α-Fe2O3, β-Fe2O3, and γ-Fe2O3 nanoparticles) or pure maghemite (γ-Fe2O3 nanoparticles) were obtained by thermal decomposition of the cubic (K-bearing) or spherical (K-free) PB particles, respectively, at 350 °C in air. The particle’s morphology of the starting material (i.e. PB) was mostly retained after the thermal decomposition. The PB samples and the as-formed iron(III) oxides were characterized by using X-ray powder diffraction (XRD), 57Fe Mössbauer spectroscopy, and scanning electron microscopy (SEM). A high amount (50 wt%) of β-Fe2O3 polymorph was produced when K-bearing PB was used, simultaneously cubic clusters of maghemite were formed. A single phase (maghemite) clustered nanoparticles with spherical morphology were obtained when we used a K-free PB. The maghemite nanoparticles (4 nm) have proven to be superparamagnetic.Keywords: Thermal decomposition, Prussian blue, iron oxides
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