A New Mode of Energy Transfer between Mn2+ and Eu2+ in Nitride-Based Phosphor SrAlSi4 N7 with Tunable Light and Excellent Thermal Stability.

In this work, reciprocal energy transfer between Mn2+ and Eu2+ ions in nitride SrAlSi4 N7 has been found and investigated in detail. In contrast to Mn2+ - and Eu2+ -activated oxide-based phosphors, the red light centered at 608 nm is ascribed to 4f-5d transitions of Eu2+ ions and Mn2+ -activated SrAlSi4 N7 emits a cyan light peaking at 500 nm. Additionally, the special broad excitation band of SrAlSi4 N7 :Mn2+ centered at 362 nm has been covered by that of Eu2+ ions ranging from 300 to 550 nm. The overlap of the energy level of Mn2+ and Eu2+ ions creates the conditions for reciprocal energy transfer between Eu2+ and Mn2+ ions. A series of SrAlSi4 N7 :0.002 Mn2+ ,xEu2+ (0≤x≤005) with tunable light emission have been synthesized and the decay curves of samples prove the reciprocal occurrence of the energy transfer between Mn2+ and Eu2+ ions. This mode of energy transfer not only prevents the loss of energy, but also improves the thermal stability, and the intensity of SrAlSi4 N7 :Mn2+ ,Eu2+ at 150 °C is still beyond 92 % of the initial intensity. The results provide a new mode of energy transfer, which is expected to reduce the drawbacks existing in energy transfer.