Synthesis of Sr(2)Si(5)N(8:)Ce(3+) phosphors for white LEDs via an efficient chemical deposition

Novel chemical vapor deposition (CVD) process was successfully developed for the growth of Sr(2)Si(5)N(8):Ce(3+) phosphors with elevated luminescent properties. Metallic strontium was used as a vapor source for producing Sr(3)N(2) vapor to react with Si(3)N(4) powder via a homogeneous gas-solid reaction. The phosphors prepared via the CVD process showed high crystallinity, homogeneous particle size ranging from 8 to 10 μm, and high luminescence properties. In contrast, the phosphors prepared via the conventional solid-state reaction process exhibited relative low crystallinity, non-uniform particle size in the range of 0.5–5 μm and relatively lower luminescent properties than the phosphors synthesized via the CVD process. Upon the blue light excitation, Sr(2−x)Ce(x)Si(5)N(8) phosphors exhibited a broad yellow band. A red shift of the emission band from 535 to 556 nm was observed with the increment in the doping amount of Ce(3+) ions from x = 0.02 to x = 0.10. The maximum emission was observed at x = 0.06, and the external and internal quantum efficiencies were calculated to be 51% and 71%, respectively. Furthermore, the CVD derived optimum Sr(1.94)Ce(0.06)Si(5)N(8) phosphor exhibited sufficient thermal stability for blue-LEDs and the activation energy was calculated to be 0.33 eV. The results demonstrate a potential synthesis process for nitride phosphors suitable for light emitting diodes.