Spectroscopy and energy transfer in lead borate glasses doubly doped with Dy(3)(+)-Tb(3+) and Tb(3)(+)-Eu(3+) ions

Energy Transfer in Dy3+ and Tb3+ Double-Doped Barium Borate Glass

In this work, single- and double-doped Dy3+ and Tb3+ barium borate glasses are investigated for their potential as light converters. The density and the absorption coefficient show linearly increasing trends with an increasing lanthanide content. The external quantum efficiency of the double-doped samples is a combination of the respective single-doped samples. The strong energy transfer from Dy3+ to Tb3+ results in an intense Tb3+-related emission, i.e., an intense green luminescence. Thus, excitation at a Dy3+-related wavelength of 452 nm enables a Tb3+-related emission, at which a single-doped Tb3+ sample barely shows any luminescence. Lifetime measurements show that there is not only an energy transfer from Dy3+ to Tb3+, but also vice versa.

Energy Transfer between Tb3+ and Eu3+ in LaPO4: Pulsed versus Switched-off Continuous Wave Excitation

The energy transfer (ET) between Tb3+ and Eu3+ is investigated experimentally and with available theoretical models in the regime of high Tb3+ concentrations in ≈30 nm LaPO4 nanoparticles at room temperature. The ET efficiency approaches 100% even for lightly Eu3+-doped materials. The major conclusion from the use of pulsed laser excitation and switched-off continuous wave laser diode excitation is that the energy migration between Tb3+ ions, situated on La3+ sites with ≈4 Å separation, is not fast. The quenching of Tb3+ emission in singly doped LaPO4 only reduces the luminescence lifetime by ≈50% in heavily doped samples. Various theoretical models are applied to simulate the luminescence decays of Tb3+ and Tb3+, Eu3+-doped LaPO4 samples of various concentrations and the transfer mechanism is identified as forced electric dipole at each ion.