Photon management in La2BaZnO5:Tm3+, Yb3+ and La2BaZnO5:Pr3+, Yb3+ by two step cross-relaxation and energy transfer

A luminescence study from UV to NIR of La2BaZnO5:Tm3+, Yb3+ and La2BaZnO5:Pr3+, Yb3+ is reported. Emission spectra of La2BaZnO5:Tm3+, Yb3+ reveal an unexpected high intensity of the Tm3+ F-3(4) -> H-3(6) emission at 5000 cm(-1) upon excitation in the Tm3+ (1)G(4) level. This unusual efficiency is explained by two successive cross-relaxation steps between Tm3+ ions, resulting in potential emission of three NIR photons for each absorbed visible photon. Emission and decay spectra of La2BaZnO5:Pr3+, Yb3+ give evidence for a Pr3+ (P-3(0) -> (1)G(4)) to Yb3+ (F-2(7/2) -> F-2(5/2)) energy transfer. The Pr3+ ((1)G(4) -> H-3(4)) to Yb3+ (F-2(7/2) -> F-2(5/2)) energy transfer could not be derived from our data. (C) 2012 Published by Elsevier B. V.