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Abstract: The spectroscopic properties of tellurite glasses of composition (in mol%) TNKNd: (70− x)TeO2–15Nb2O5–15K2O–xNd2O3 (x =0.1, 1.0, 1.5, 2.0 and 2.5) and TNLNd10: 69TeO2–15Nb2O5–15Li2O–1.0Nd2O3 and lithium metaborate glass of composition LBNNd10: 89LiBO2–10Nb2O5–1.0Nd2O3 have been investigated using absorption and emission spectra and decay curve analysis. An energy level analysis has been carried out considering the experimental energy positions of the absorption and emission bands, using the free-ion Hamiltonian model. The spectral intensities have been calculated by using the Judd–Ofelt theory and in turn the radiative properties such as radiative transition probabilities, emission cross-sections, branching ratios and radiative lifetimes have been estimated. The decay curves at the lower concentrations are exponential while they show a non-exponential behavior at higher concentrations (⩾1.0mol%) due to energy transfer processes. The effective lifetimes for the 4F3/2 level are found to decrease with increase in Nd2O3 concentration for all the glasses under investigation. The non-exponential decay curves have been well-fitted to the Yokota–Tanimoto model with S =6, indicating that the nature of energy transfer is of dipole–dipole type and energy migration also plays an important role. The results obtained have been compared with Nd3+-doped phosphate, fluorophosphate, lead borate, tellurite, germanate and silicate glasses and Nd3+-doped YAG ceramic and Ca2Nb2O7 crystals. [Copyright &y& Elsevier]

Abstract: This article reports the effect of mixed alkalis on the optical absorption and emission spectra of Sm3+ and Dy3+ doped chloroborate glass matrices of the compositions 69.5B2O3 xLiCl(30− x)NaCl0.5R2O3 and 69.5B2O3 xLiCl(30− x)KCl0.5R2O3 (where R=Sm and Dy and x =5, 10, 15, 20 and 25). Using Judd–Ofelt theory, the spectral intensities and Judd–Ofelt intensity parameters (Ω 2, Ω 4 and Ω 6) were obtained from the measured absorption bands of the spectra. Using these intensity parameters, total radiative transition probabilities (A T), radiative lifetimes (τ R), branching ratios (β) and peak emission cross-sections (σ P) were obtained for the two rare earth ions in these two glass matrices. Variation of these parameters with x in the glass matrix has been discussed. It is found that for Sm3+ ion, the transition, 4G5/2 → 6H9/2 shows highest emission cross-section and is maximum at x =10mol% in lithium–sodium and at x =20mol% in lithium–potassium glass matrices. For Dy3+ ion, the transition, 4F9/2 → 6H13/2 shows highest emission cross-section and is maximum at x =20mol% in lithium–sodium and at x =10mol% in lithium–potassium glass matrix. [Copyright &y& Elsevier]