Upconversion Luminescence Properties of Ho3+/Tm3+/Yb3+ Co-doped NaGd(MO4)2 Prepared by Hydrothermal Method

In this paper, Ho$$^{3+}$$/Tm$$^{3+}$$/Yb$$^{3+}$$-doped NaGd(MO$$_{4})_{2}$$ phosphors were prepared using the hydrothermal method and the effect of Yb$$^{3+}$$ doping amount on the luminescence properties of these phosphor materials was investigated. NaGd(MO$$_{4})_{2}$$ was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and spectral analysis. The results showed that Ho$$^{3+}$$/Tm$$^{3+}$$/Yb$$^{3+}$$-doped NaGd(MO$$_{4})_{2}$$ has tetragonal phase structures, and doping with rare-earth ions decreases the cell parameters of NaGd(MO$$_{4})_{2}$$. NaGd(MO$$_{4})_{2}$$:Ho$$^{3}$$/Tm$$^{3+}$$/Yb$$^{3+}$$ generates blue, green, and red lights at 477, 545, and 659 nm, respectively, under an excitation of 980 nm. The emission of these three lights is called a three-photon process. As the doping ratio of Yb$$^{3+}$$ increases, the colour coordinates of samples gradually approach the white region from the red region, enabling NaGd(MO$$_{4})_{2}$$:0.1Ho/1Tm/20Yb to exhibit white emission. Doping with Yb$$^{3 + }$$ increases the energy transfer and quantum efficiencies of NaGd(MO$$_{4})_{2}$$. When the concentration of Yb$$^{3+}$$ reached 30%, the quantum efficiency of NaGd(MO$$_{4})_{2}$$ reached the maximum value of 188.37%. Overall, NaGd(MO$$_{4})_{2}$$:Ho/Tm/Yb has broad application prospects in the field of white lighting.