Upconversion luminescence of (Lu,M)NbO4:Yb3+,Er3+ (M: Al3+, Ga3+)

The effects of substitution of Al3+ and Ga3+ ions on the upconversion luminescence of (Lu,M)NbO4:Yb3+,Er3+ (M: Al3+, Ga3+) were studied for the first time. Under infrared (980 nm) radiation, the upconversion spectra consisted of strong green and weak red emission bands, which were assigned to the transition of the H-2(11/2)/S-4(3/2) and F-4(9/2) levels, respectively, to the ground state (I-4(15/2)) of the Er3+ ions through an energy transfer process from Yb3+ to Er3+. A two-photon upconversion process was involved in the upconversion emission of (Lu,M)NbO4:Yb3+,Er3+. Substitution of Al3+ and Ga3+ ions increased the green (red) emission intensity to approximately 120% (120%) and 135% (130%), respectively. These behaviors were explained in terms of the crystal field asymmetry and energy transfer probability. (C) 2017 Elsevier Ltd. All rights reserved.