NMR and Mössbauer Study of Al2O3–Eu2O3

Abstract

Alumina-europia mixed oxides with 5 and 10 wt.% Eu 2 O 3 were studied by Mössbauer spectroscopy, 27 Al MAS-NMR and X-ray diffraction (XRD). The samples were prepared by the sol-gel technique. The XRD patterns for the calcined samples show a broad peak around 2q = 30-which is assigned to the Eu 2 O 3 ; after treatment with hydrogen at 1073 K no reduction to Eu +2 or Eu 0 was observed. The NMR spectra show three peaks, which are assigned to the octahedral, pentahedral and tetrahedral aluminum sites; the intensity of each peak depends on the concentration of europium ions. The Mössbauer spectra of the calcined samples show a single peak near zero velocity which is attributed to the Eu +3 ; after H 2 treatment at 1073 K similar spectra were obtained, suggesting Eu +3 is not reducibly at this temperature.

A Study of the Influence of Composition on the Microstructural Properties of ZnO/Al2O3 Mixed Oxides

“…Generally, three differently coordinated Al species are found in γ‐Al 2 O 3 . Octahedrally, pentahedrally, and tetrahedrally coordinated Al can be assigned to peaks in 27 Al MAS NMR experiments at chemical shifts in the range of δ = –20 to 20 ppm, 25–40 ppm, and 45–80 ppm, respectively 48–51. Correspondingly three Al species are detected in the pure Al 2 O 3 sample Zn00‐c with peaks at chemical shifts of δ = 8 ppm, 36 ppm, and 67 ppm.…”

The effect of Al-doping on ZnO nanoparticles applied as catalyst support

“…The spectrum is dominated by a narrow signal at a chemical shift of 81 ppm, which is assigned to Al in the well-defined tetrahedral environment of the ZnO lattice. 18 It is noted that a significant fraction of Al was also present in octahedral (signal at 7 ppm) and poorly defined five-fold coordination (signal near 46 ppm [33][34][35] ). These less well-defined Al species may be present in small amounts of X-ray amorphous Al-rich by-phases.…”