Dual-wavelength responsive color-tunable upconversion luminescence in Na(Y, Gd)F4: Yb3+, Er3+ phosphors

A series of Na(Y, Gd)F4:Yb3+,Er3+ phosphor samples co-doped with different concentrations of Gd3+, Yb3+ and Er3+ ions were synthesized at 550 °C for 2 h by a solid-state reaction method. The crystal structure and upconversion (UC) luminescence properties of the samples upon 980/1550 nm wavelength excitation were characterized by XRD and emission spectral analysis methods. The XRD analysis showed that the synthesized samples were all pure hexagonal β-NaYF4 phase. The doping of Gd3+ ions into β-NaYF4 solid solution matrix can obviously enhance the UC luminescence intensity of the NaYF4: Yb3+, Er3+ samples both upon 980 and 1550 nm laser diode excitation. Moreover, the UC emission of the 1550 nm excited Na(Y, Gd)F4:Yb3+,Er3+ samples had a better color tunability than that of the UC emission of the 980 nm excited samples. Meanwhile, based on the experimental results, the UC luminescence mechanisms of the sample upon 980 and 1550 nm excitation were also discussed.