Temperature-dependent luminescence and energy transfer in Europium and rare-earth-codoped nanostructured sol-gel SiO 2 glasses

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ABSTRACTTemperature- dependent luminescence spectra, lifetimes and energy transfer in Eu3 and other rare earths codoped sol-gel Si02 glasses, were investigated in the temperature rangefrom 1 OK to 300K. Due to the addition of the other rare earths as co-dopants, luminescence spectra of Eu haveshown significant changes not only in spectral intensities but also in emission peak features. Evaluation of thetemperature- dependent energy transfer rates and lifetimes and the computation of critical energy transfer distancesby employing two different energy transfer model schemes, have provided evidence for such luminescence behaviorin the nanometer- size confined glass matrices.Keywords: Eu3 sol-gel glasses, luminescence spectra, energy transfer 1. INTRODUCTION Sol-gel glasses have been considered to be more promising and strategic materials to realize quantum confinedluminescence phenomena and as new phosphor materials for high density TV and compact lasers.1'2 Sol gel methodprovides a convenient alternative to the traditional melting method for the preparation of rare earth ions dopedglasses for optical studies, this method permits lower temperature processing, higher sample homogeneity and purityand the opportunity to prepare a variety of new optical materials in both bulk and film form with ease. There hasbeen a great deal of interest in the luminescence of impurity ions doped sol-gel Si02 glasses in which bright emissionin the visible spectral regions has been observed at room temperature due to ligand to metal charge transfer.3 Strongsurface effects and nanometer size limited optical properties have been reported for sol-gel glasses.47 Excitationenergy transfer processes of rare earth ions in conventional glasses have also been reported in literature.8, However,no report has so far been made available in literature on energy transfer of rare earth ions in sol gel glasses. Keepingin view of the technological importance of these sol-gel materials, it would therefore be of more interest to studysystematically the excitation energy transfer in such rare earth ions co-doped glasses which possess nano-structurednetworks. In the present paper, we report the luminescence spectra and decay profiles of Eu3 ions co-doped glasses.