Syntheses and photoluminescence properties of Eu²⁺/Tb³⁺ doped Sr₂Si₅N₈ phosphors

Eu²⁺/Tb³⁺ doped Sr₂Si₅N₈ phosphors were prepared by carbothermal reduction and nitridation method. The luminescence of Tb³⁺/Eu²⁺ co-doped Sr₂Si₅N₈ were investigated. The experimental results indicated that owing to spin-allowed f → d transition rule the four emission lines located at 490, 543, 585, and 623 nm which ascribed to the ⁵D₄→⁷F_j (j = 6, 5, 4, 3) transitions were observed under 330 nm excitation. No obvious changes in spectral line shape were observed for Sr₂Si₅N₈:Eu²⁺ co-doped with Tb³⁺. However, the emission intensity was improved by about 20% with Tb³⁺ doping concentration of x = 0.01 mainly because of the electric multipole energy transfer from Tb³⁺ to Eu²⁺.