6533b7d1fe1ef96bd125c0ba

RESEARCH PRODUCT

Up-conversion processes in NaLaF4:Er3+

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abstract Structural and spectroscopic investigation of NaLaF 4 :Er 3+ material at different doping concentrations ispresented. X-ray diffraction patterns, up-conversion luminescence spectra and decay curves for 2 H 9/2 ? 4 I 15/2 , 4 S 3/2 ? 4 I 15/2 and 4 F 9/2 ? 4 I 15/2 optical transitions in the material are shown and possibleexcitation routes are discussed. Raman spectrum for the undoped material is presented and the effectivephonon energy of the material is estimated. Based on the obtained results application of rare-earth dopedNaLaF 4 in the field of up-conversion phosphors is evaluated. 2009 Elsevier B.V. All rights reserved. 1. IntroductionFor many years rare-earth (RE) doped materials have beenbroadly used in a variety of applications. Owing to their abundantstructure of energy levels many fields of science and technologylike solid-state lasers, colour displays, optical telecommunicationutilize the unique properties of these materials [1–3]. For somedecades much attention has been paid for studies of up-conversion(UC) processes in RE doped materials, whichinvolve the absorptionof several photons (usually IR) and subsequent emissionof one sin-gle photon (VIS or UV) [4]. UC effect could be used in differentareas like solid-state lasers[5], temperaturesensors[6], white lightsimulation [7], improvement of the efficiency of solar cells [8] andothers.The efficiency of the UC process strongly depends on the rate ofradiationless transitions within RE ion and therefore on the pho-non energy of the medium: the higher the phonon energy (e.g.the higher rate of radiationless transitions), the lower the effi-ciency of UC. Most fluoride crystals (LaF