Study of Defect Sites in Ce_1–xM_xO_2−δ (x = 0.2) Solid Solutions Using Raman Spectroscopy

Abstract

A series of Ce(1-x)M(x)O(2-δ) (M = Gd, Zr, La, Sm, Y, Lu, and Pr) samples were characterized by Raman spectroscopy to investigate the evolution of defect sites (oxygen vacancies and MO(8)-type complex) and their distributions in the samples. It was found that the evolution of oxygen vacancies was due to the different ionic valence state of dopant from that of Ce(4+), while the evolution of the MO(8)-type complex was due to the different ionic radius of dopant from that of Ce(4+). The distributions of defect sites were investigated using 325 and 514 nm excitation laser lines, indicating that the defect sites were surface enriched. Moreover, the increasing ordering level of the sample led to a decline in the concentration of the MO(8)-type complex in the sample but the constant concentration of oxygen vacancies, implying that the metastable MO(8)-type complex species were more disordered compared to the oxygen vacancies.

In Operando Raman Spectroscopy Study on Oxygen Chemical Potential Change in Ni−SDC Cermet Anode for Solid Oxide Fuel Cells

“…complexes. [27][28][29] In this study, however, the intensity of the band at ca. 600 cm −1 was very weak.…”

New Ionic Conductor as Solid Electrolyte for Solid Oxide Fuel Cell Application

“…With the substitution of yttrium by lanthanum, the band at ~610 cm -1 disappears. This band has been related to the presence of MO 8 -type complex defect, that occurs as a result of the difference between the ionic radius of dopants and the radius of Ce 4+ [19]. From these results it is possible to verify the effective incorporation of the oxygen vacancies in the CeO 2 crystalline structure.…”

“…Raman spectral features of the doped ceria are quite different when different excitation laser lines are used. This occurs due the distinct detection depth of the excitation laser which reflects the inhomogeneous distribution of dopants in the sample [19,20]. For this reason we used a 632.8 nm excitation laser line that reflects both the interior and the surface information of the sample due to the weak absorption of the La and Y doped ceria at this wavelength [19].…”

“…This occurs due the distinct detection depth of the excitation laser which reflects the inhomogeneous distribution of dopants in the sample [19,20]. For this reason we used a 632.8 nm excitation laser line that reflects both the interior and the surface information of the sample due to the weak absorption of the La and Y doped ceria at this wavelength [19]. The Raman mode observed nearly 460 cm -1 is attributed to F 2g vibrational mode, which is characteristic of fluorite structure.…”

Synthesis of 1,3-Diols from Isobutene and HCHO via Prins Condensation-Hydrolysis Using CeO2 Catalysts: Effects of Crystal Plane and Oxygen Vacancy

“…The oxygen vacancies detected by Raman spectroscopy are primarily those on several surface layers of the CeO 2 . The ratio of the integrated peak areas (A 595 /A 462 ) was used to quantify the relative concentrations of oxygen vacancy [53]. The relative oxygen vacancy concentration of CeO 2 samples are shown in Table 1 and Figure S3.…”