Synthesis and Luminescence Properties of Orange–Red‐Emitting M ₂ Si ₅ N ₈ :Eu ²⁺ (M=Ca, Sr, Ba) Light‐Emitting Diode Conversion Phosphors by a Simple Nitridation of MSi ₂

Eu ²⁺ ‐doped M ₂ Si ₅ N ₈ (M=Ca, Sr, Ba) orange–red phosphors were successfully prepared by a simple, direct, and efficient solid‐state reaction using air‐stable MSi ₂ , Eu ₂ O ₃ , and α‐Si ₃ N ₄ as the starting materials under N ₂ –H ₂ (5%) atmosphere. The influence of the type of the alkaline‐earth ion on the phase structure and luminescence properties has been investigated. The results show that the synthesized powders have a single‐phase crystal structure of M ₂ Si ₅ N ₈ for M=Ca, Sr, and a little amount of BaSi ₇ N ₁₀ impurity phase for M=Ba. Under the blue light excitation, M ₂ Si ₅ N ₈ :Eu ²⁺ shows a typical broad band emission of Eu ²⁺ ranging from orange to red (585–620 nm) depending on the type of M ion. The emission intensity, conversion efficiency, and thermal stability increase with the sequence of Ca<Ba<Sr, which suggests that Sr ₂ Si ₅ N ₈ :Eu ²⁺ has the highest application potential as a red conversion phosphor for white light‐emitting diodes.