Facile preparation and formation mechanism of Sr₂Si₅N₈:Eu²⁺ red-emitting phosphors

The red-emitting Sr 2 Si 5 N 8 :Eu 2+ phosphors have been synthesized in a new facile process using (oxy)nitride precursors by inductive calcination under N 2 atmosphere at ordinary pressure. Different from the prevailing methods, lower cost raw materials, simpler pretreatment, without harsh conditions and a shorter reaction time are achieved. It was found that red-emitting Sr 2 Si 5 N 8 :Eu 2+ phosphors were synthesized with high crystallinity and purity after 1 h inductive calcination. The formation mechanism was characterized by XRD, SEM, TEM and Fluorescence microscopy. It was demonstrated that a hexagonal mesophase of Sr-doped α -Si 3 N 4 was primarily formed in the reaction process, which transformed into the final product of the orthorhombic Sr 2 Si 5 N 8 :Eu 2+ phosphors. During the reaction process, the color of the samples transforms from greenish-yellow to orange and eventually to red. The as-prepared phosphors have a wide excitation in the range of 250 ∼ 570 nm which matches blue light chips and give a red-light emission peaking at 610 nm. The results indicate a promising prospect for a simple, efficient and inexpensive way to prepare Sr 2 Si 5 N 8 :Eu 2+ phosphors for blue/UV-based warm-white LEDs and other fluorescent applications.