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 2 Si 5 N 8 :Eu 2+ has the highest application potential as a red conversion phosphor for white light‐emitting diodes.