Fig. 1. X-ray diffraction pattern of Li(Y_1-xGd_x)_0.79F₄∶Yb³⁺/Ho³⁺

Fig. 2. SEM spectrum of the sample
(a): Gd³⁺ doping concentration is 0 mol%; (b): Gd³⁺ doping concentration is 30 mol%;(c): Gd³⁺ doping concentration is 50 mol%

Fig. 3. (a) Li(Y_1-xGd_x)_0.79F₄∶Yb³⁺/Ho³⁺ micro-crystal fluorescence spectrum; (b) Li(Y_1-xGd_x)_0.79F₄∶ Yb³⁺/Ho³⁺ micro-crystal luminescence under 980 nm excitation

Fig. 4. (a) 0 and 30 mol% concentration of Gd³⁺ ion doped LiYF₄∶ Yb³⁺/Ho³⁺ micron crystal Up-conversion luminescence; (b) Li(Y_1-xGd_x)_0.79F₄∶ Yb³⁺/Ho³⁺ micron crystal energy level transition diagram

Fig. 5. Upconversion fluorescence lifetime of LiYF₄∶Yb³⁺/Ho³⁺ microparticle crystals doped with 0 mol% Gd³⁺ and 30 mol% Gd³⁺ ions

Fig. 6. (a) Different concentrations of Gd³⁺ ion doped LiYF₄∶Yb³⁺/Ho³⁺ micro-crystal luminescence intensity graph; (b) red luminescence intensity ratio R% (R%=I_{630~665 nm}/I_{450~770 nm}) and green luminescence intensity ratio G%(G%=I_{525~560 nm}/I_{450~770 nm})

Fig. 7. (a) Fluorescence spectrum of 980nm laser with excitation power of 0.5~1.5 W; (b) ratio of red to green luminous intensity when excitation power is 0.5~1.5 W (R/G=I_{630~665 nm}/I_{525~560 nm})

Fig. 8. (a) Screen printing process diagram of anti-counterfeiting pattern; (b) Screen printing up-conversion light-emitting anti-counterfeiting pattern