Effects of doped-Li+ and -Eu3+ ions content on structure and luminescent properties of LixSr1−2x(MoO4):Eu3+x red-emitting phosphors for white LEDs

Eu3+-activated molybdate-based red-emitting phosphors of LixSr1−2x(MoO4):Eu3+x with various doped-ions contents (x = 0.1–0.5) were synthesized by the organic gel-thermal decomposition process and their structure and photoluminescence properties were investigated. The as-synthesized phosphors are characterized with a scheelite structure and almost tetragonal-dipyramidal morphology. With the doped-ions content increasing from (x=) 0.1 to 0.5 in LixSr1−2x(MoO4):Eu3+x, the lattice cell reduces and the grain growth is basically suppressed during the calcination process owing to the hybrid ions substitution. These LixSr1−2x(MoO4):Eu3+x phosphors can be effectively excited by ultraviolet light (396 nm) and blue light (466 nm), which are well suitable for current commercial near-UV and blue LEDs. The excitation intensity and emission intensity for LixSr1−2x(MoO4):Eu3+x phosphors exhibit an increasing trend with the doped-ions content, and two maximum values are located at x = 0.25 and 0.45 respectively, which are coincident with two minimum average grain sizes about 76 nm (x = 0.25) and 58 nm (x = 0.45) calculated by the X-ray diffraction analysis. The measured chromaticity coordinates for LixSr1−2x(MoO4):Eu3+x phosphors with a high doped-ions content (x = 0.25–0.50) are completely consistent with the National Television System Committee (NTSC) standard requirement.