Characterization and magnetic performance of pure CeO2 nanoparticles via an ozonolysis reaction

CeO2 nanoparticles were prepared via an ozonolysis assisted co-precipitation method at room temperature (referred to as O3-CeO2) and were calcined at 300 °C for 3 h (referred to as O3-CeO2-300). CeO2 nanoparticles were also prepared by a co-precipitation method with no ozonolysis for comparison (referred to as CeO2-300). The prepared samples were characterized to determine their phase, morphology, functional groups, surface area, valence states and magnetic properties using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller analysis, X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometry, respectively. The samples exhibited XRD peaks and TEM-selected area electron diffraction corresponding to face centered cubic CeO2, confirming a single phase. The average crystallite sizes were in the range of 8.0 ± 0.3 to 12.0 ± 0.4 nm. TEM imagery revealed a morphological transformation from irregular shapes into hexagonal-like CeO2 when examining O3-CeO2 and O3-CeO2-300 samples, respectively. XPS results showed Ce states in the form of Ce4+ and Ce3+ and oxygen vacancies were observed in all samples. All samples exhibited weak ferromagnetic behavior at room temperature with a maximum magnetization value of 3.6 × 10-3 Am2/kg for O3-CeO2-300. The origin of the ferromagnetism in pure CeO2 is explained on the basis of an F-center exchange mechanism via ferromagnetic Ce3+ (↑↑) coupling