Microwave sol-gel synthesis and upconversion photoluminescence properties of CaGd2(WO4)(4):Er3+/Yb3+ phosphors with incommensurately modulated structure

摘要

CaGd2-x(WO4)(4):Er3+/Yb3+ phosphors with the doping concentrations of Er3+ and Yb3+ (x=Er3++Yb3+, Er3+=0.05, 0.1, 0.2 and Yb3+=0.2, 0.45) have been successfully synthesized by the microwave sol-gel method. The crystal structure of CaGd2-x(WO4)(4):Er3+/Yb3+ tungstates have been refined, and upconversion photoluminescence properties have been investigated. The synthesized particles, being formed after the heat-treatment at 900 degrees C for 16 h, showed a well crystallized morphology. Under the excitation at 980 nm, CaGd2(WO4)(4):Er3+/Yb3+ particles exhibited a strong 525-nm and a weak 550-nm emission bands in the green region and a very weak 655-nm emission band in the red region. The Raman spectrum of undoped CaGd2(WO4)(4) revealed about 12 narrow lines. The strongest band observed at 903 cm(-1) was assigned to the v(1) symmetric stretching vibration of WO4 tetrahedrons. The spectra of the samples doped with Er and Yb obtained under the 514.5 nm excitation were dominated by Er3+ luminescence preventing the recording of these samples Raman spectra. Concentration quenching of the erbium luminescence at H-2(11/2)-> I-4(15/2) transition is weak in the range of erbium doping level x(Er)=0.05-0.2, while, for transition S-4(3/2)-> 4I(15/2), the signs of concentration quenching become pronounced at x(Er)=0.2. (C) 2015 Elsevier Inc. All rights reserved.