Tunable luminescence of LiY9(SiO4)6O2:Ce3+-Tb3+-Sm3+ phosphors for LED and temperature-sensing applications

The multifunctional Ce3+/Tb3+/Sm3+ doped LiY9(SiO4)6O2 (LYSO) phosphors were prepared by conventional high-temperature solid-state reaction, and their luminescence properties for LEDs and optical thermometers were investigated. The phase purity was checked by XRD patterns and the morphology feature was learned by SEM and TEM techniques. First, under 350 nm excitation, the Ce3+-activated LYSO exhibits broad emission band from 370 to 600 nm, and the optimal Ce3+ doping content was determined to be 2 mol%. By monitoring different emission wavelengths of Ce3+, the excitation spectra were found to be different, which could be owing to more than one Ce3+ emission center. The Ce3+-Tb3+ codoped LYSO phosphors were designed to realize tunable emission, where the energy transfer based on dipole-dipole interaction was verified by using spectra and decay curves. White emitting light was obtained finally in the Ce3+-Tb3+-Sm3+ tridoped LYSO sample with the chromaticity coordinates (x = 0.305, y = 0.357), and the excellent thermally luminescent stability was found. Second, upon 295 nm excitation, it has been observed that the thermal quenching properties of Ce3+ and Tb3+ are different in the codoped sample, which creates a changing luminescence intensity ratio (LIR) for Ce3+ and Tb3+. The corresponding temperature sensing properties were evaluated.