Eu3+ luminescence in aluminophosphate glasses

With a 4f(6) electronic configuration, europium ions in the trivalent charge state are known to be efficient activators in wide band gap matrices. Embedded in the aluminophosphate (Li2O-BaO-Al2O3-La2O3-P2O5) glasses the optically activated Eu3+ ions lead to intense room temperature orange/red luminescence with 16-23 Cd/m(2) by using ultraviolet pumping. The as-prepared and heat treated europium doped glasses for temperatures below and above T-g were studied by room temperature Raman spectroscopy, absorption, photoluminescence excitation, temperature dependent and time dependent photoluminescence. When the samples are excited by 325 nm wavelength photons, an enhancement of the red luminescence intensity by ca. one order of magnitude was found to occur for temperatures between 14 K and 350 K, for all the doped glasses. On the other hand, by using resonant excitation on the L-5(6) Eu3+ excited state (lambda(exc)similar to 390 nm) the ion emission intensity was found to be nearly constant for temperatures up to 500 K. For higher temperatures a steeper decrease of the luminescence intensity occurs due to non-radiative competitive channels described by activation energies of ca. 235 meV and 450 meV by using 325 and 390 nm wavelength photons as excitation, respectively. The lifetime of the D-5(0) level in these glasses is ca. 2.93 ms. A discussion of the thermal population and de-excitation mechanisms is performed. (C) 2013 Elsevier B.V. All rights reserved.