Structure and photoluminescence properties of Ce³-doped novel silicon-oxynitride Ba_4-zM_zSi₈O _20-3xN_2x (M=Mg, Ca, Sr)

Structural and photoluminescence properties of undoped and Ce ³-doped novel silicon-oxynitride phosphors of Ba_4-zM _zSi₈O_20-3xN_2x (M=Mg, Sr, Ca) are reported. Single-phase solid solutions of Ba_4-zM_zSi ₈O_20-3xN_2x oxynitride were synthesized by partial substitutions of 3O^2-→2N^3- and Ba→M (M=Mg, Ca, Sr) in orthorhombic Ba₂Si₄O₁₀. The influences of the type of alkaline earth ions of M, the Ce³ concentration on the photoluminescence properties and thermal quenching behaviors of Ba₃MSi₈O_20-3xN_2x (M=Mg, Ca, Sr, x=0.5) were investigated. Under excitation at about 330 nm, Ba ₃MSi₈O_20-3xN_2x:Ce³ (x=0.5) exhibits efficient blue emission centered at 400450 nm in the range of 350650 nm owing to the 5d→4f transition of Ce³. The emission band of Ce³ shifts to long wavelength by increasing the ionic size of M due to the modification of the crystal field, as well as the Ce³ concentrations due to the Stokes shift and energy transfer or reabsorption of Ce³ ions. Among the silicon-oxynitride phosphors of Ba ₃MSi₈O_18.5N:Ce³, M=Sr _0.6Ca_0.4 possesses the best thermal stability probably related to its high onset of the absorption edge of Ce³.