Cooperative up-conversion in Eu3+,Yb3+-doped SiO2-PbO-PbF2-CdF2 oxyfluoride glass

Novel oxyfluoride glass doped with YbF3 and Eu2O3 is synthesized in the SiO2-PbO-PbF2-CdF2 system by melt-quenching technique. Its physical properties, as well as the optical absorption of Eu3+ and Yb3+ ions are studied. Spectroscopic properties of Eu3+ ions are modeled within modified Judd-Ofelt theory, yielding absorption oscillator strength, luminescence branching ratios and radiative lifetime of D-5(0) state. Intrinsic emission of Eu3+ ions under direct excitation in the UV, as well as up-conversion luminescence under near-IR excitation via cooperative energy transfer, 2Yb(3+) -> Eu3+, are studied. In the latter case, the glass provides intense reddish-orange emission with CIE coordinates x = 0.636,y = 0363. The asymmetry parameter R for Eu3+ emission in the studied glass is about 8. The efficiency of this transfer mechanism is estimated from shortening of F-2(5/2)(Yb3+) lifetime to be 10 +/- 1%. (C) 2014 Elsevier B.V. All rights reserved.