Influence of acceptor concentration on crystallization behavior and luminescence properties of lead borate glasses co-doped with Dy3+ and Tb3+ ions

Lead borate glasses doubly doped with Dy3+-Tb3+ were investigated using optical spectroscopy: photoluminescence and decay time measurements. The main green emission band due to the 5D4→7F5 transition of Tb3+ was observed under excitation of Dy3+. The energy transfer process from Dy3+ to Tb3+ occurs through nonradiative processes. The energy transfer efficiencies and transfer probabilities as a function of a square of the total rare earth ions concentration using Förster method were calculated. The nonlinear behavior of the energy transfer probability and the luminescence intensity ratio for a higher concentration of acceptor was studied taking into account the possible processes: concentration quenching and partial crystallization of the lead borate glasses.