A New Mode of Energy Transfer between Mn 2+ and Eu 2+ in Nitride-Based Phosphor SrAlSi 4 N 7 with Tunable Light and Excellent Thermal Stability.

In this work, reciprocal energy transfer between Mn ²⁺ and Eu ²⁺ ions in nitride SrAlSi ₄ N ₇ has been found and investigated in detail. In contrast to Mn ²⁺ - and Eu ²⁺ -activated oxide-based phosphors, the red light centered at 608 nm is ascribed to 4f-5d transitions of Eu ²⁺ ions and Mn ²⁺ -activated SrAlSi ₄ N ₇ emits a cyan light peaking at 500 nm. Additionally, the special broad excitation band of SrAlSi ₄ N ₇ :Mn ²⁺ centered at 362 nm has been covered by that of Eu ²⁺ ions ranging from 300 to 550 nm. The overlap of the energy level of Mn ²⁺ and Eu ²⁺ ions creates the conditions for reciprocal energy transfer between Eu ²⁺ and Mn ²⁺ ions. A series of SrAlSi ₄ N ₇ :0.002 Mn ²⁺ ,xEu ²⁺ (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 Mn ²⁺ and Eu ²⁺ ions. This mode of energy transfer not only prevents the loss of energy, but also improves the thermal stability, and the intensity of SrAlSi ₄ N ₇ :Mn ²⁺ ,Eu ²⁺ 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.
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