Study of Defect Structure in Ferromagnetic Nanocrystalline CeO₂: Effect of Ionic Radius

Abstract

In this study, the relationship between defect structure and magnetic behavior of La-doped CeO 2 nanoparticles (NPs) was investigated systematically. The doping level ranges from 0% to 15%. X-ray Absorption Spectroscopy (XAS) and Raman spectroscopy were utilized to investigate the electronic structure of these NPs. It is demonstrated that oxygen vacancy was increased upon doping with La. The major oxygen vacancy defect structure was M 3+ -V O -M 3+ (M: Ce or La) in lightly doped NPs while it changes to La 3+ -V O -La 3+ as the doping level reaching 7%. Scanning transmission electron microscopy coupled with electron energy loss spectroscopy (STEM/EELS) analysis showed that in La-doped NPs, both the dopant (La 3+ ) and Ce 3+ distributed rather homogenously within the NPs, which is different to other doped ceria including Y, Sm and Cr doped ones where a strong interaction between surface, trivalent cerium and dopant were reported. The distinct distribution of defect was attributed to the larger ion radius of La and the nature of La related oxygen vacancy. Moreover, room temperature ferromagnetism (FM) is observed in these La doped ceria but with a weaker intensity when compared to the magnetism obtained for other doped ceria NPs with similar dopant concentration. It indicates that high concentration of defects and dopant at surface is critical to obtain larger FM.

Magnetic Properties of Rare Earth Doped SnO2, TiO2 and CeO2 Nanoparticles

“… (for x = 2; 4; 6; 8; 10% − = 33; 35; 40; 46; 55 meV, respectively). This leads to increasing of the magnetization M (see Figure ) what is in qualitative agreement with the experimental data of Rakhmatullin et al Lee et al reported also an increase of the magnetization M with increasing of Ce 3+ ions. But Lee et al showed that as the content of Y 3+ is enhanced, the concentration of Ce 3+ increases for and then begins to decrease for .…”

“…The RTFM in SnO 2 , TiO 2 , CeO 2 , and ZnO NPs is investigated also by doping with rare earth (RE) ions by many authors . The aim of the present study are the oxide SnO 2 , TiO 2 and CeO 2 NPs.…”

Achieving ferromagnetic insulating properties in La0.9Ba0.1MnO3 thin films through nanoengineering

“…We note that the CeO 2 phase is fully relaxed (data not shown here) in the ip direction due to the large lattice mismatch with STO (>1%), and therefore, the ip strain was not considered when inferring the Ce doping ratio from the op lattice constant. Ladoped CeO 2 can be regarded as a dilute magnetic oxide but the magnetization is usually at least two orders of magnitude lower than in manganites, 59,60 and hence its contribution to the overall magnetic signal is insignificant.…”

Lanthanide (III) (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) Ions Loaded in CeO2 Support; Fundamental Natures, Hydrogen Reduction, and CO Oxidation Activities

“…This could be related with the ionic radius dependent CeO 2 crystal lattice [17,34]. Upon metal ion loading, additional Raman peaks were commonly observed between 500 and 650 cm -1 , attributed to oxygen vacancies (and/or crystal lattice distortions) created by metal doping [14,16,20,30]. Bare CeO 2 , the defect-related Raman peak was found to be extremely weak.…”

“…under nitric acid solutions, and observed higher CO oxidation activity, attributed to higher oxygen vacancies, Cu + species, and improved dispersion of active Cu species and reducibility of CeO 2 catalyst [14]. Vacancy formation is also known to be highly dependent on the dopant ionic radius [15][16][17]. Chen [20].…”