Multicolor Emission in a Single-Phase Phosphor Ca_3Al_2O_6:Ce~(3+),Li~+:Luminescence and Site Occupancy

摘要

A single-phase multicolor emitting phosphor, Ca_3Al_2O_6:Ce~(3+), Li+, was prepared by a solid-state reaction. When the Ce3 + concentration is lower than 0.030 (molar ratio in Ca_3Al_2O_6), yellow and greenish blue emissions can be observed under the excitation by a blue and a near UV light, respectively. The yellow-emitting phosphor possesses an internal quantum efficiency of 89%. Additional purplish blue emission turns up when Ce~(3+) concentrations are higher than 0.040. Tunable emission bands are originated from Ce~(3+) ions on different Ca sites in Ca_3Al_2O_6. Although the emission band of purplish blue or greenish blue overlaps the excitation band of yellow emission, and the distances between the unlike Ce~(3+) ions are in the range of electric dipole-dipole interaction, no energy transfer is observed. Furthermore, emission wavelengths for the yellow, greenish blue, and purplish blue emission show little change upon increasing Ce~(3+) concentrations.