The effect of cation modifier on improving the luminescent properties of borate glasses doped with Yb3Â + and Er3Â +

In this work we present the preparation and characterization of new fluoroborate glasses doped with Yb3 + and Er3 + and modified by Ca, Sr and Ba oxides. Glasses with compositions (100-x-y) (MO ⋅ 2B2O3) + x NaF + y (YbF3:ErF3) (% in mol), where M is Sr, Ba, Ca, x = 10-30% and y = 0, 1 or 5% were prepared by the melt/quenching technique. Glass forming ability and stability were studied by thermal analysis and it is shown that calcium samples presented the highest stability. The nature of the modifier cation has also shown a direct influence on the absolute and relative intensities of the rare earth ions transitions in the visible and near-infrared regions. Though the calcium samples present lower absorption intensities, they display the best up- and down-conversion efficiencies. There are evidences that the incorporation of the fluoride compound leads to a fluorine rich environment on the first coordination sphere of the RE, decreasing the probability of OH- groups - well known quenchers of RE emissions. Though preliminary, the results in this study can become of relevance for the field of solar cell technology improvement via betterment of solar light harvesting in the infrared and ultraviolet regions.