Structural and luminescence behavior of lead fluoroborate glasses containing Eu3+ ions

Structural and luminescence behavior of lead fluoroborate glasses prepared with the chemical composition (50−x)B2O3+20PbO+20PbF2+10ZnO+xEu2O3 (where x  =0.05, 0.1, 0.5, 1, 2 and 3 in wt%) have been studied by varying the trivalent europium ion content. Structural behavior of the prepared glasses has been explored through XRD, FTIR and Raman spectral analysis. Optical characterization has been made using UV–vis–NIR absorption, excitation, luminescence and decay curves of the present glasses. Through the absorption spectra, bonding parameters (β¯ and δ) have been determined and the positive value of δ indicates the covalent nature. The band gap values are found to decrease with increasing Eu3+ ion concentration whereas Urbach's energy values are found to increase. The PSB associated with the 7F0→5D2 excitation transition is used to determine the electron–phonon coupling constant and the local structure of the Eu3+ ions with its surrounding ligands. The luminescence intensity ratio of the 5D0→7F2 to 5D0→7F1 transition has been calculated to estimate the local site symmetry around the Eu3+ ions. Judd–Ofelt (J–O) intensity parameters Ωλ (λ=2,4,6) were obtained from the emission spectra and the same is used to estimate the transition probability (A  ), stimulated emission cross-section (σPE) and branching ratios (βR) for the excited levels of the Eu3+ ions. The decay profiles were found to be single exponential for all the title glasses. The higher values of A  , σPE and βR corresponding to the 5D0→7F2 emission level at 614 nm confirm the potential of the present glasses as a red laser active medium.