Spectroscopic investigations of Pr3+ ions in Na2O-La2O3-ZnO-TeO2 glasses

Tellurite glasses of the composition xPr6O11-(7 − x)La2O3-3Na2O-25ZnO-65TeO2 (where x = 0.005, 0.01, 0.1, 0.2, 0.5, 1.0 and 2 mol%) were obtained by the melt quenching technique. Absorption (300 K), excitation (300 K) and fluorescence spectra (at 77 and 300 K) as well as fluorescence decay curves of the Pr3+-doped title glasses are presented and discussed. Basing on the Judd-Ofelt analysis, the phenomenological Judd-Ofelt parameters (Ω2 = 2.13, Ω4 = 16.8 and Ω6 = 3.50 × 10−20 cm2), radiative transition probabilities (AT), branching ratios (β), radiative lifetimes (τR) and emission cross-sections (σem) were calculated for the luminescence from 3P1, 3P0, 1D2 and 1G4 levels of the Pr3+ ion. The fluorescence from the 1G4 level of the Pr3+ ion has been observed after excitation at 445 nm in the 3P2 state. The experimental lifetimes of the emission levels indicate strong concentration quenching. An analysis of non-radiative decay of the 1D2 level indicate that energy migration via a diffusion limited relaxation and cross-relaxation processes are involved in the depopulation of this level. The spectroscopic results show that the investigated glasses are potentially candidates as at 1.3 μm and 1.45 μm laser host as well as reddish-orange to yellow tunable phosphor. Furthermore, a near-infrared downconversion process gives possibility of using of these materials as luminescent solar concentrators and near infrared lasers.