Spectroscopic properties of KGd(WO4)2 single crystals doped with Er3+, Ho3+, Tm3+ and Yb3+ ions: Luminescence and micro-Raman investigations

KGd(WO4)(2) single crystals doped with Ho3+/Yb3+/Er3+ and Ho3+/Tm3+/Yb3+/Er3+ ions were grown by means of the Top Seeded Solution Growth (TSSG) method. It was shown that these systems exhibit multicolor up-conversion luminescence in the visible and near-infrared spectral ranges under 980 nm laser excitation. In the investigated crystals the Yb3+ ions were used as the energy sensitizer ion and the up-converted luminescence originates from transitions between the energy levels of other co-doped rare earth ions such as Er3+, Ho3+ or Tm3+, which play the role of the energy activator ions. The vibrational properties of the crystals were investigated using micro-Raman spectroscopy and the role of vibrational energy in the effective energy transfer process between the rare earth ions was discussed. The proposed combinations of activator ions may be suitable for gaining novel materials with effective green, red and near-infrared emission. (C) 2013 Elsevier B.V. All rights reserved.