Tb3+ as a probe for the molecular structure of mixed barium magnesium alumino silicate glasses

Abstract

Two series of mixed barium magnesium alumino silicate glasses with the molar compositions (35-x) BaO·x MgO·10 Al2O3 ⋅55 SiO2 (mol%) (peralkaline series: x = 0, 2.5, 5, 7.5, 10, 15, 25, 35) and (20-x) BaO·x MgO·20 Al2O3 ⋅60 SiO2 (mol%) (metaluminous series: x = 0, 10, 20) have been prepared and doped with Tb3+ ions with a constant concentration of 1·1020 cm−3. Despite the constant doping concentration in all samples, the Tb3+ luminescence spectra and lifetimes show clear and systematic effects depending on the BaO/MgO and (BaO+MgO)/Al2O3 ratios in the samples. For the peralkaline glass series with 35 mol% network modifier oxides, the strong effect on the luminescence emission peak ratios and the Stark splitting of the emission peaks points to a strong influence of the network modifying ions and systematic changes in the Tb-Tb distances. For the metaluminous series with 20 mol% network modifier oxides and 20 mol% Al2O3, these changes are comparably small.The Tb3+ luminescence lifetimes increase with increasing BaO concentrations in the peralkaline series but decrease in the metaluminous series. All effects are discussed with respect to the local surrounding of the doped Tb3+ ions.