Low-Temperature Synthesis of Sr2Si5N8:Eu2+ Red-Emitting Phosphor by Modified Solid-State Metathesis Approach and Its Photoluminescent Characteristics

Sr 2 Si 5 N 8 :Eu 2+ red-emitting nitridosilicate phosphor was prepared by a low temperature modified solid-state metathesis (MSSM) approach. The method is based on the nitridation of strontium chloride in presence of silicon and lithium nitrides. Lithium nitride was used as a solid source of nitrogen and as reduction agent for strontium chloride. We revealed that the formation of Sr 2 Si 5 N 8 occurs via solid+liquid mechanism through intermediate SrSiN 2 phase and found that Sr 2 Si 5 N 8 :Eu 2+ can be synthesized by MSSM approach starting at a considerably low temperature (1100°C). We first showed the possibilities of using flux materials during the synthesis of complex alkaline earth-based nitfidosilicates. The phosphor particles synthesized at optimized condition (1300°C and 6 hours) show a rod-like morphology in 1∼5 μm width and 5―10 μm length. The color coordinate (CIE) of Sr 2 Si 5 N 8 :Eu 2+ (2 wt%) are (0.6382; 0.3612) and emission spectrum exhibits a broad-band peaking at 628 nm. The synthesized phosphor was applied to LED package and white light has been obtained with CCT ∼ 4700 K and R a ∼ 90―92 depending on driving current. The MSSM method has proven to be a cost-effective and facile way to prepare nitridosilicate phosphor with outstanding performance. An approximate chemical pathway for Sr 2 Si 5 N 8 :Eu 2+ formation is proposed.