Tunable Luminescence and Energy Transfer of Sr 3 B 2 O 6 :Ce 3+ , Sm 3+ Phosphors with Potential Anti-Counterfeiting Applications.

Sm 3+ and Ce 3+ singly doped and Sm 3+ and Ce 3+ co-doped Sr 3 B 2 O 6 phosphors are prepared via a high-temperature solid-state reaction method. The crystal structure and phase purity are characterized by X-ray diffraction (XRD) analyses. The Sm 3+ -doped sample displays an emission in the orange-red region, with the strongest emission line at about 648 nm and possessing a good luminescence thermal stability between 78 and 500 K. With the increase in the Sm 3+ content, the concentration quenching is observed due to the cross-relaxation (CR) processes among the Sm 3+ ions. Upon 340 nm excitation, the Ce 3+ -doped phosphor presents a broad emission band in the blue region with a maximum at about 420 nm, which overlaps well with the 6 H 5/2 → 6 P 3/2 excitation line of Sm 3+ and implies the possible energy transfer from Ce 3+ to Sm 3+ . The spectral and decay measurements of the Ce 3+ and Sm 3+ co-doped samples are conducted and the Inokuti-Hirayama (I-H) model is adopted to analyze the luminescence decay dynamics of the donor Ce 3+ . Owing to the evident sensitization of the Sm 3+ by the Ce 3+ ions, the co-doped samples exhibit color variation under different wavelength excitations, endowing them with potential applications in optical anti-counterfeiting.