Tunable Luminescence and Energy Transfer of Sr3B2O6:Ce3+, Sm3+ Phosphors with Potential Anti-Counterfeiting Applications

Abstract

Sm³⁺ and Ce³⁺ singly doped and Sm³⁺ and Ce³⁺ co-doped Sr₃B₂O₆ 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 Sm³⁺-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 Sm³⁺ content, the concentration quenching is observed due to the cross-relaxation (CR) processes among the Sm³⁺ ions. Upon 340 nm excitation, the Ce³⁺-doped phosphor presents a broad emission band in the blue region with a maximum at about 420 nm, which overlaps well with the ⁶H_5/2 → ⁶P_3/2 excitation line of Sm³⁺ and implies the possible energy transfer from Ce³⁺ to Sm³⁺. The spectral and decay measurements of the Ce³⁺ and Sm³⁺ co-doped samples are conducted and the Inokuti-Hirayama (I-H) model is adopted to analyze the luminescence decay dynamics of the donor Ce³⁺. Owing to the evident sensitization of the Sm³⁺ by the Ce³⁺ ions, the co-doped samples exhibit color variation under different wavelength excitations, endowing them with potential applications in optical anti-counterfeiting.

Keywords: Ce3+; Sm3+; energy transfer; optical anti-counterfeiting; tunable luminescence.