Changing Ce³⁺ Content and Codoping Mn²⁺ Induced Tunable Emission and Energy Transfer in Ca_2.5Sr_0.5Al₂O₆:Ce³⁺,Mn²⁺

A series of color-tunable Ce³⁺ single-doped and Ce³⁺, Mn²⁺ codoped Ca_2.5Sr_0.5Al₂O₆ phosphors were synthesized by a high-temperature solid-state reaction. The crystal structure, luminescent properties, and energy transfer were studied. For Ca_2.5Sr_0.5Al₂O₆: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 Ca_2.5Sr_0.5Al₂O₆ 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 Ca_2.5Sr_0.5Al₂O₆:0.11Ce³⁺,<i>x</i>Mn²⁺ 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 Ca_2.5Sr_0.5Al₂O₆:Ce³⁺,Mn²⁺ phosphor is a promising candidate for near UV-excited w-LEDs