A New Mode of Energy Transfer between Mn2+ and Eu2+ in Nitride‐Based Phosphor SrAlSi4N7 with Tunable Light and Excellent Thermal Stability

In this work, reciprocal energy transfer between Mn²⁺ and Eu²⁺ ions in nitride SrAlSi₄N₇ 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 SrAlSi₄N₇ emits a cyan light peaking at 500 nm. Additionally, the special broad excitation band of SrAlSi₄N₇: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 SrAlSi₄N₇:0.002 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 SrAlSi₄N₇: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.