Al NMR studies of Ce-Al mixed oxides: origin of 40 ppm peak |
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Authors: | R SasikalaV Sudarsan SK Kulshreshtha |
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Institution: | Novel Materials and Structural Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India |
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Abstract: | CeO2-γ-Al2O3 mixed oxides have been prepared by using both co-precipitation and impregnation methods followed by calcination at 650°C and investigated by 27Al MAS NMR, powder X-ray diffraction and temperature programmed reduction techniques to understand the nature of chemical interaction existing between CeO2 and γ-Al2O3. The 27Al NMR spectra of CeO2-containing samples showed an additional peak placed at 40 ppm along with the two peaks at 68 and 6 ppm which originate from the tetrahedrally and octahedrally coordinated Al3+ ions present in γ-Al2O3. As the concentration of CeO2 in the mixed oxide increased, the intensity of the 40 ppm peak increased and this was the prominent peak for CeO2-rich mixed oxide samples. The origin of this 40 ppm peak is discussed and it is inferred that this peak is due to Al3+ ions, which are present in CeO2 lattice, forming a solid solution. |
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Keywords: | CeO2 Al2O3 27Al NMR 40 ppm peak X-ray diffraction TPR |
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