Positron annihilation spectroscopic studies on Nd-doped ceria

Synthesis and characterization of Th1−xLnxO2−x/2 mixed-oxides

“…This structure was stabilized up to x Nd 0.42. As detailed elsewhere [32][33][34][35][74][75][76], the stabilization of the fluorite crystal symmetry despite the incorporation of an aliovalent cation was presumably made possible thanks to the concomitant creation of randomly distributed oxygen vacancies. Weak additional XRD lines located at about 208 and 428 (as pointed out by stars in Fig.…”

“…This crystal structure was stabilized during the incorporation of trivalent elements up to about 50 at.% of the cations for La or Nd [20,21] and to less than 10 at.% of Yb or Lu [18,19]. The incorporation of trivalent elements was examined thanks to the use of fluorite-type Hf 1Àx Ln x O 2Àx/2 [25,26], Zr 1Àx Gd x O 2Àx/2 [27][28][29], or Ce 1Àx Ln x O 2Àx/2 [30][31][32][33][34][35][36][37][38][39][40] solid solutions analogues with the help of several techniques (molecular dynamics [29,32], life-time positon spectroscopy [33], EXAFS [34] or m-Raman spectroscopy [35][36][37][38][39][40]). All these techniques suggested the existence of a mechanism involving the concomitant creation of oxygen vacancies (V Ö ) to counterbalance the lack of positive charges due to the incorporation of the trivalent lanthanide.…”

Shape-dependent interplay between oxygen vacancies and Ag–CeO2 interaction in Ag/CeO2 catalysts and their influence on the catalytic activity

“…This clearly demonstrates that the Ag-CeO 2 interaction exerts great influences on the structure of CeO 2 nanocrystals. PALS, a well-established technique to study defects in materials [21,[50][51][52][53][54][55], was employed to further probe the structure of oxygen vacancies in various samples. Fig.…”

“…CeO 2 nanorods exhibit two components with the lifetime of 262 (s 1 ) and 397 ps (s 2 ). The s 2 component corresponds to the annihilation of positrons in large oxygen vacancy clusters in CeO 2 while the s 1 component arises from the annihilation of positrons in small oxygen vacancies in CeO 2 such as Ce 3+ -oxygen vacancy associates and mono-vacancies[21,52,53]. Therefore, PALS results demonstrate that CeO 2 nanocubes and nanorods are with different structures of oxygen vacancies.…”

Fabrication of a PdAg mesocrystal catalyst for the partial hydrogenation of acetylene

“…Thus the relative intensities (I) of s 1 , s 2 , and s 3 provide information about the relative concentration of different defects [65,66]. The value of I 2 (33.68 %) and the ratio I 2 /I 1 (0.57) for PdAg MCs/HT catalyst are both higher than the corresponding values for PdAg NPs/HT (32.66%, 0.53), which may indicate that the concentration of defect sites is higher in the MCs than in the NPs.…”