Synthesis and luminescence properties of Yb3+, Tm3+ and Ho3+ co-doped SrGd2(WO4)2(MoO4)2 nano-crystal

Abstract

Novel up-conversion luminescent SrGd2(WO4)2(MoO4)2: Yb3+/Tm3+/Ho3+ nano-crystals were synthesized by hydrothermal method. The composition ratio of rare earth had been investigated. It indicated that when CYb3+ = 10 mol% and CYb3+/CTm3+/CHo3+ = 10:1.5:2, the emission intensities were the highest. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and up-conversion luminescence spectra were used to characterize SrGd2(WO4)2(MoO4)2: Yb3+/Tm3+/Ho3+ nano-crystals and they showed that the sample had high degree of crystallinity, the sample was tetragonal system, and the grain size of the sample was about 56 nm. Three emission peaks, including blue emission peak, green emission peak and red emission peak were observed at 477, 543 and 651 nm corresponding to 1G4 → 3H6 and 1G4 → 3F4 transitions of Tm3+, 5F4 → 5I8 and 5F5 → 5I8 transitions of Ho3+ respectively. All the emission peaks were observed by excitation of 980 nm semiconductor laser. The relationship between up-conversion intensity and excitation power revealed that blue emission at 477 nm was a three-photon absorption process, green emission at 543 nm and red emission at 651 nm was a two-photon absorption process. The quantum yields of the sample were near 3.2%.