Effect of Fe2+ (Fe3+) Doping on Structural Properties of CeO2 Nanocrystals

Abstract

We have measured the Raman scattering and magnetization of pure and Fe2+(Fe3+) doped CeO2 nanopowders at room temperature. The Raman scattering spectra revealed the existence of CeO2 fluorite cubic structure for all investigated samples. The Raman active mode at about 600 cm(-1), seen in all samples, can be ascribed to the CeO2 intrinsic oxygen vacancies. Additional Raman modes at 720 cm(-1), 1320 cm(-1) and 1600 cm(-1), which appear in the spectra of doped samples, can be assigned to maghemite (gamma-Fe2O3) cation deficient structure, to 2 omega(LO) IR-allowed overtone and two magnon structure, respectively. This implies that our powders are composed of mixed valence states and have defective structure. Presence of oxygen defect states and magnetic ions can be responsible for the observed ferromagnetism at room temperature in both pure and Fe doped samples.