Influence of Cr3+ ions doping on growth and upconversion luminescence properties of β-NaYF4:Yb3+/Er3+ microcrystals

beta-NaYF4:Yb3+/Er3+ microcrystals codoped with Cr3+ ions were prepared for the first time via a facile hydrothermal method. The influence of doping concentration of Cr3+ ions on growth and upconversion (UC) luminescence properties of beta-NaYF4:Yb3+/Er3+ microcrystals were investigated in detail. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra and photoluminescence (PL) spectra were used for characterization. The results demonstrated that the morphology and size of beta-NaYF4:Yb3+/Er3+ microcrystals were influenced by doping concentration of Cr3+ ions, the possible mechanism was proposed. The UC intensity of beta-NaYF4:Yb3+/Er3+ microcrystals was significantly enhanced by doping of Cr3+ ions. In contrast to beta-NaYF4:Yb3+/Er3+ microcrystals without doping of Cr3+ ions, the green and red emission intensities of the microcrystals codoped with 15 mol% Cr3+ ions were enhanced by 16 and 7 times, respectively. The enhancement of the UC intensities should be ascribed to the distortion of local symmetry around Er3+ ions, the UC mechanism was discussed. This work will be helpful for improving the UC intensity of other lanthanide-doped UC nano-and micro-crystals. (C) 2015 Elsevier B.V. All rights reserved.