(Color online) (a) XRD patterns for pure ceria samples. Through the Scherrer relation, the average size of the particles was determined to be about 4 nm for all three samples. (b)-(c) TEM image and diffraction pattern with size distribution.
(a)-(c) show the change in lattice parameters for Fe-doped samples of Ce-Cl, Ce-Nit, and Ce-AmNit methods, respectively, with a linear fit applied. All three methods showed a strong “dip” in the lattice parameter for x < 2.5%, indicated by a drop line at 2.5%. For Ce-Cl–prepared samples, there was a more stable linear decline in the lattice parameter. This trend also appears to be present in the other two methods.
(Color online) (a) Fe 3p peak positions from XPS analysis of Fe-doped Ce-AmNit samples. The three drop lines indicate the reported Fe 3p peak positions of Fe3+ in Fe2O3 and two Fe2+ positions reported for FeO at 55.4, 54.9, and 54.5 eV, respectively (Ref. 14). (b) Fe 3p peaks for iron-doped Ce-Cl samples with drop lines corresponding to the ones mentioned in (b). Peak positions for Fe2O3 and FeOOH established from Ref. 14 and curve fits from Refs. 2 and 3.
(Color online) (a) XPS Ce3d spectral region for three 1% Fe-doped samples. (b) EPR spectra for 1% and 5% Fe-doped Ce-Cl samples recorded at T ∼ 5 K.
(Color online) (a)-(b) Magnetization and moment of Ce-Cl samples. (c)-(d) Magnetization and moment of Ce-Nit and Ce-AmNit samples.
Average saturation magnetization Ms of Fe-doped ceria samples prepared using the three methods vs the Ce3+/4+ ratios along with a linear fit shown for the three points. Ce3+/4+ ratios were determined from XPS analysis (Ref. 15).
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