Changing Ce3+ Content and Codoping Mn2+ Induced Tunable Emission and Energy Transfer in Ca2.5Sr0.5Al2O6:Ce3+,Mn2.

A series of color-tunable Ce3+ single-doped and Ce3+, Mn2+ codoped Ca2.5Sr0.5Al2O6 phosphors were synthesized by a high-temperature solid-state reaction. The crystal structure, luminescent properties, and energy transfer were studied. For Ca2.5Sr0.5Al2O6:Ce3+ phosphors obtained with Al(OH)3 as the raw material, three emission profiles were observed. The peak of photoluminescence (PL) spectra excited at ∼360 nm shifts from 470 to 420 nm, while that of the PL spectra excited at 305 nm stays unchanged at 470 nm with the increase of Ce3+ content. Furthermore, the peak of PL spectra is situated at 500 nm under excitation at ∼400 nm. The relationship between the luminescent properties and crystal structure was studied in detail. Ce3+, Mn2+ codoped Ca2.5Sr0.5Al2O6 phosphors also showed interesting luminescent properties when focused on the PL spectra excited at 365 nm. Obvious different decreasing trends of blue and cyan emission components were observed in Ca2.5Sr0.5Al2O6:0.11Ce3+,xMn2+ phosphors with the increase in Mn2+ content, suggesting different energy transfer efficiencies from blue- and cyan-emitting Ce3+ to Mn2+. Phosphors with high color-rendering index (CRI) values are realized by adjusting the doping content of both Ce3+ and Mn2+. Studies suggest that the Ca2.5Sr0.5Al2O6:Ce3+,Mn2+ phosphor is a promising candidate for near UV-excited w-LEDs.