Emission features of Ho ion in Nb2O5, Ta2O5 and La2O3 mixed Li2O-ZrO2-SiO2 glasses |
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Authors: | T. SrikumarM.G. Brik Ch. Srinivasa RaoN. Venkatramaiah Y. GandhiN. Veeraiah |
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Affiliation: | a Department of Physics, Acharya Nagarjuna University-Nuzvid Campus, Nuzvid 521201, A.P., India b Institute of Physics, University of Tartu, Riia 142, Tartu 51014, Estonia c Department of Chemistry, Pondicherry University, Pondicherry, India |
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Abstract: | Li2O-ZrO2-SiO2: Ho3+ glasses mixed with three interesting d-block elemental oxides, viz., Nb2O5, Ta2O5 and La2O3, were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature. The luminescence spectra of Nb2O5 and Ta2O5 mixed Li2O-ZrO2-SiO2 glasses (free of Ho3+ ions) have also exhibited broad emission band in the blue region. This band is attributed to radiative recombination of self-trapped excitons (STEs) localized on substitutionally positioned octahedral Ta5+ and Nb5+ ions in the glass network. The Judd-Ofelt theory was successfully applied to characterize Ho3+ spectra of all the three glasses. From this theory various radiative properties, like transition probability A, branching ratio βr and the radiative lifetime τr, for 5S2 emission levels in the spectra of these glasses have been evaluated. The radiative lifetime for 5S2 level of Ho3+ ions has also been measured and quantum efficiencies were estimated. Among the three glasses studied the La2O3 mixed glass exhibited the highest quantum efficiency. The reasons for such higher value have been discussed based on the relationship between the structural modifications taking place around the Ho3+ ions. |
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Keywords: | Li2O-ZrO2 boldFont" >-(Nb2O5 Ta2O5 and La2O3) boldFont" >-SiO2: Ho3+ glasses Spectroscopic properties Quantum efficiency |
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