Tunable Luminescence and Energy Transfer of SrBO:Ce, Sm Phosphors with Potential Anti-Counterfeiting Applications.

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