Luminescence from Ce in sol–gel SiO2

The sol–gel process provides an attractive low temperature alternative to the melt process for producing Ce-doped silica, but reports of the emission wavelength have not been consistent. In this paper, luminescence measurements using a variety of excitation methods, including cathodoluminescence not...

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Published inPhysica. B, Condensed matter Vol. 407; no. 10; pp. 1595 - 1598
Main Authors Kroon, R.E., Seed Ahmed, H.A.A., Ntwaeaborwa, O.M., Koao, L.F., Nagpure, I.M., Gusowski, M.A., Botha, J.R., Swart, H.C.
Format Journal Article Conference Proceeding
LanguageEnglish
Published Kidlington Elsevier B.V 15.05.2012
Elsevier
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Summary:The sol–gel process provides an attractive low temperature alternative to the melt process for producing Ce-doped silica, but reports of the emission wavelength have not been consistent. In this paper, luminescence measurements using a variety of excitation methods, including cathodoluminescence not yet reported by other researchers, are compared and evaluated in the light of previously published data. Several papers report luminescence around 350nm but emission near this wavelength was not found from our samples. This luminescence originates from Ce that has not yet been incorporated in the silica and is found in samples that have not undergone high temperature annealing. Our photoluminescence results from samples annealed in a reducing atmosphere suggest that emission from Ce incorporated in the silica lattice occurs near 455nm, and some indication of the emission from Ce in amorphous clusters at 400nm is also found. However, our results also confirm earlier indications that intrinsic defects in silica can create photoluminescence near both these wavelengths, which can make identification of the luminescence due to Ce difficult. Finally, it has been found that samples which have been annealed in air, and therefore display poor photoluminescence because most of the Ce occurs in the tetravalent form, are luminescent under electron beam excitation. It is suggested that during cathodoluminescence measurements Ce4+ ions capture electrons to form excited Ce3+ ions from which the luminescence originates.
Bibliography:ObjectType-Article-2
SourceType-Scholarly Journals-1
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content type line 23
ISSN:0921-4526
1873-2135
DOI:10.1016/j.physb.2011.09.094