Structural and luminescence investigations on Sm3+ doped sodium fluoroborate glasses containing alkali/alkaline earth metal oxides

Structural and luminescence behavior of the Sm3+ doped 49B2O3+25xCO3+25NaF+1Sm2O3, (where x=Li2, Na2, K2, Ca and Mg) glasses have been studied and reported. Structural analysis of the prepared glasses was made through FTIR spectra and their optical properties were studied using optical absorption, luminescence and lifetime measurements. The bonding parameters and the oscillator strengths were determined from the absorption spectra. These parameters have been used to obtain the Judd−Ofelt parameters. Using the Judd−Ofelt parameters, radiative properties such as transition probability (A  ), stimulated emission cross section (σPE) and branching ratio's (βR) for the trivalent samarium ions corresponding to their 4G5/2→6HJ (J=5/2, 7/2, 9/2 and 11/2) excited state transitions have been calculated and reported. The decay curve of the 4G5/2→6H7/2 transition exhibits non−exponential behavior. The non-exponential behavior has been attributed to the energy transfer through cross-relaxation between adjacent Sm3+ ions. The lifetime of the 4G5/2 level is found to be comparatively less than that of the reported Sm3+ glasses and the same is due to the presence of OH groups, which is confirmed through the FTIR spectral studies.

Research Highlights
► The amorphous nature was confirmed by XRD studies and the FTIR studies indicate the O−H, B−O bonds of the trigonal BO3 units and the B−O−B linkages.
► Studies on bonding parameters through absorption spectra confirms the Sm–ligand bond is of ionic nature.
► The fall in Ωλ may be due to the increase in ionicity between Sm−ligand bond and further confirmed through bonding parameters and the increase in symmetry around Sm3+ ion.
► In the present study, Sm3+:BLNS glass exhibits larger σPE and higher βR values suggesting the same to be used for laser applications.
► The value of τexp is found to be lower, leading to relatively low value of η due to the presence of OH groups in the glasses, which is confirmed through IR spectra.