Effect of defects and oxygen vacancies on the RTFM properties of pure and Gd-doped CeO2 nanomaterials through soft XAS

Abstract

This work primarily is an investigation of the electronic structure properties of pure CeO2 and $${Ce}_{1-x}{Gd}_{x}{O}_{2}$$ (x = 0.02, 0.04, 0.06, 0.08 and 0.10) Nanoparticles using the soft X-ray absorption spectroscopy were used to explore defects and vacancies. For this purpose, pure CeO2 and $${Ce}_{1-x}{Gd}_{x}{O}_{2}$$ (x = 0.02, 0.04, 0.06, 0.08 and 0.10) nanomaterials were synthesized using the co-precipitation method. The XAS spectra at Ce M4,5, O K-edge and Gd M4,5 absorption edges clearly indicated a decrease in the valence state of Ce ions from Ce4+ to Ce3+ with the formation of oxygen vacancy defects upon incorporation of Gd3+ ions in CeO2 nanolattice. The results show meagre and sparse segregations of additive Gd+3 ions to form secondary phases in the samples. The deconvoluted Ce M4,5 peaks and O K-edge peaks clearly showed the existence of both oxidation states of Ce ions, Ce3+ and Ce4+,and also indicated the formation of oxygen vacancy defects in all the samples. The presence of Gd3+ oxidation state of Gd ions in Gd+3-doped CeO2 samples was investigated through Gd M4,5 edges. Furthermore, the origin of ferromagnetism in pure CeO2 and Gd3+-doped CeO2 samples is explained using F-centre exchange mechanism mediated by defects and oxygen vacancies.