Tunable emissions in single-phase La_9.33Si₆O₂₆:Ce³⁺,Tb³⁺,Sm³⁺ phosphors for multifunctional applications

Emission-tunable La_9.33Si₆O₂₆:Ce³⁺,Tb³⁺,Sm³⁺ (LS:Ce³⁺,Tb³⁺,Sm³⁺) phosphors were designed by solid-state reaction for different applications. Their photoluminescence (PL) properties under ultraviolet light excitation were studied in detail. The single-phase structures were determined by the XRD patterns. The PL spectra of the Ce³⁺-activated samples exhibited broad luminescence bands, where two different Ce³⁺ emission centers were determined. In the Ce³⁺-Tb³⁺ codoped samples, an efficient energy transfer (ET) was witnessed with the spectral characteristics and decay curves. Owing to this ET, the emission color can be tuned from bluish violet to light green. When the Ce³⁺-Tb³⁺-Sm³⁺ ions were tri-doped, two ET processes for Ce³⁺ → Sm³⁺ and Tb³⁺ → Sm³⁺ appeared simultaneously. As a result, the white emission was successfully achieved in the LS:0.5%Ce³⁺,4%Tb³⁺,3%Sm³⁺ phosphor. The thermally luminescent stability revealed that the thermal quenching temperature T_0.5 of this phosphor is higher than many other reported phosphors. The device fabrication was made with the LS:Ce³⁺,Tb³⁺,Sm³⁺ phosphor, which can show visible or invisible pattern depending on the excitation light. The above investigations indicate that the developed LS:Ce³⁺,Tb³⁺,Sm³⁺ phosphors have potential applications in white LEDs and anticounterfeiting.