Upconversion Luminescence Properties of YF3: Er3+, Yb3+ Doped with Al3+, Ba2+

Upconversion materials of YF3: Er3+, Yb3+ doped with Al3+, Ba2+ were prepared by high temperature solid state method in order to enhance emission intensities in the field of laser anti-counterfeit. Al3+ and Ba2+ could cause host lattice shrinking, reduce local crystal field symmetry around rare earth ions, increasing the intra 4fN transition probabilities. The 548 nm green and 660 nm red emission intensities of samples doped with 1.7%Al3+ (mole fraction) were 1.1 and 1.4 times as strong as the ones without Al3+ respectively according to upconversion emission spectra under 980 nm excitation. The green and red emission intensities of samples doped with 0. 8%Ba2+ (mole fraction) were 2.8 and 2.2 times as strong as the ones without Ba2+ respectively. The Ba2+ contents had effects on crystal phases with X-ray diffraction (XRD). The results of differential thermal analysis (DTA), emission spectra, XRD, scanning electron microscope (SEM) showed that optimal sintering temperature was 955℃ where optimal luminescence properties, crystallinities, grain growth appeared for samples with the optimal doping contents. Luminescence mechanisms of 548 nm green and 660 nm red emissions were discussed with fluorescent lifetime curves and fitting results of upconversion emission intensity and excitation current. Energy level transition processes were represented for YF3: Er3+, Yb3+ materials under 980 nm excitation. © 2018, Science Press. All right reserved.