Structure and photoluminescence properties of Ce3+-doped novel silicon-oxynitride Ba4−zMzSi8O20−3xN2x (M=Mg, Ca, Sr)

Structural and photoluminescence properties of undoped and Ce3+-doped novel silicon-oxynitride phosphors of Ba4−zMzSi8O20−3xN2x (M=Mg, Sr, Ca) are reported. Single-phase solid solutions of Ba4−zMzSi8O20−3xN2x oxynitride were synthesized by partial substitutions of 3O2−→2N3− 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 Ba3MSi8O20−3xN2x (M=Mg, Ca, Sr, x=0.5) were investigated. Under excitation at about 330 nm, Ba3MSi8O20−3xN2x:Ce3+ (x=0.5) exhibits efficient blue emission centered at 400–450 nm in the range of 350–650 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 Ba3MSi8O18.5N:Ce3+, M=Sr0.6Ca0.4 possesses the best thermal stability probably related to its high onset of the absorption edge of Ce3+.