Structure and photoluminescence of polymer-derived Pr-doped SiAlON red phosphor

The praseodymium (Pr)-doped silicon based aluminum oxynitride (SiAlON) red phosphors were prepared by a novel polymer-derived method using polycarbosilane and acetylacetonates as the starting materials. The organic precursors containing Pr and Al were formed via polymer reactions at 320 degrees C, followed by nitridizing with NH3 at 800 degrees C for the organic-inorganic transformation, and finally by sintering under N-2 at 1650 degrees C for the crystallization. Accordingly, the chemical composition, surface morphology, crystal structure and photoluminescence property of the polymer-derived Pr-doped SiAlON phosphors were studied. The strong red emission was observed at 623 nm under the excitation of 290 nm with the average decay time of 30 mu s, corresponding to D-1(2) -> H-3(4) transition. The empirical formula was determined to be Si3.0Al0.2O0.3N3.0C0.03Pr0.02, which is Si rich with trace amount of C. The main crystal phase was identified as hexagonal beta-(Si,Al)(3)(O,N)(4):Pr with a space group P6(3). Each Pr ion was located in the lattice along c-axis by coordinating with three nearest N/O atoms in the neighboring plane. In addition, the amorphous Si rich components were also presented. Possible impure phases, accounted for less than 5%, might include SiC, (Pr-2(Al0.5Si2.5O3.5N3.5) and PrSi3N5.