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

Tellurite glasses of the composition xPr(6)O(11)-(7- x)La2O3-3Na(2)O-25ZnO-65TeO(2) (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 (Omega(2) = 2.13, Omega(4) = 16.8 and Omega(6) = 3.50 x 10(-20) cm(-2)), radiative transition probabilities (A(T)), branching ratios (beta), radiative lifetimes (tau(R)) and emission cross-sections (sigma(em)) were calculated for the luminescence from P-3(1), P-3(0), D-1(2) and (1)G(4) levels of the Pr3+ ion. The fluorescence from the (1)G(4) level of the Pr3+ ion has been observed after excitation at 445 nm in the P-3(2) state. The experimental lifetimes of the emission levels indicate strong concentration quenching. An analysis of non-radiative decay of the D-1(2) 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 mu m and 1.45 mu m 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.