ZHANG Lei, FAN Yalei, HUANG Yuexia, WANG Deqiang
(School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China)

Abstract: YF₃ : Er³⁺，Yb³⁺ materials doped with Mg²⁺ were synthesized by high temperature solid state method so as to enhance emission intensities for laser anti-counterfeit applications. The 548 nm green and 660 nm red emission intensities of the samples doped with 1.0mol% Mg²⁺ were 1.5 and 1.4 times as strong as the ones without Mg²⁺ respectively according to the upconversion emission spectra under 980 nm diode laser excitation. Mg²⁺ could cause lattice shrinking, reduce crystal field symmetry around Er³⁺ and Yb³⁺, increasing the 4f-4f transition probabilities. The influence of the Mg²⁺ content on crystalline phases was characterized by X-ray diffraction (XRD). The results of differential thermal analysis (DTA), emission spectra, XRD, and scanning electron microscope (SEM) showed among all the samples with 1.0mol% Mg²⁺ but sintered at different temperatures those sintered at 940 °C had the optimal emission intensities, crystallinities and grain growth. The upconversion luminescence mechanisms of 548 nm green and 660 nm red emission were discussed with fluorescent lifetime curves and fitting results of emission intensity and excitation current. Energy level transition processes were analyzed for YF₃ : Er³⁺, Yb³⁺ materials under 980 nm excitation.

Key words: YF₃; upconversion; Er³⁺; doped