Structural and luminescence behavior of Sm3+ ions doped lead boro-telluro-phosphate glasses

Abstract

The Sm3+ ions doped lead boro-telluro-phosphate glasses with the chemical composition 30H3O3+(20–x)PbO+15TeO2+10P2O5+10ZnO+15BaCO3+xSm2O3 (x=0.05, 0.1, 0.25, 0.5, 1.0 and 2.0 in wt%) have been prepared by a melt quenching technique and their structural and optical behavior were studied and reported. The physical properties like, refractive index, density and dielectric constant etc., have been estimated. FTIR and Raman spectral studies have been made to explore the presence of functional groups and various structural units in the prepared glasses. The formation of bridging and non-bridging oxygens of BO4, BO3, TeO3, TeO6 and PbO4 structural units have been investigated. From the absorption spectra, the direct (n=1/2), indirect (n=2) band gap, band tailing parameter (B) and Urbach energy (ΔE) values were estimated. The ionic nature of the metal–ligand bond in the title glasses has been discussed. The Judd–Ofelt intensity parameters (Ωλ,λ=2, 4, and 6), oscillator strength of ƒ−ƒ electric dipole transitions and transition probability (A) have been evaluated. The predicted radiative lifetime (τrad) and branching ratio (βR) values of the 4G5/2 excited level of the Sm3+ ions to the lower energy levels were determined and compared with the experimentally measured values. From the recorded fluorescence spectra, the strong transitions of Sm3+ ions 4G5/2→6H5/2 (565nm), 4G5/2→6H7/2 (602nm), 4G5/2→6H9/2 (648nm) and a weak transition, 4G5/2→6H11/2 (709nm) have been observed. The significant laser parameters like, gain bandwidth (σpE×λeff), optical gain (σpE×τrad) and stimulated emission cross-section (σpE) values were estimated for the 4G5/2→6HJ (J=5/2, 7/2, 9/2 and 11/2) emission transitions. The decay profile of the present glasses reveal the single exponential nature at small concentrations (≤0.25%) and non-exponential at higher concentrations (≥0.5%) due to cross-relaxation and non-radiative energy transfer processes and the same has been discussed using I–H model. The 0.5wt% of the Sm3+ ions doped lead boro-telluro-phosphate glasses exhibit reddish orange luminescence indicating its usefulness for the development of optical, display and LED devices.