Preparation Eu-doped ca-α-SiAlON phosphor by heterogeneous precipitation: An orange–yellow phosphor for white light-emitting diodes

In this research, Ca-α-SiAlON phosphors with compositions of Ca1−xEuxSi9Al3ON15 (x=2.5%, 5.0%, 7.5%, 10.0% and 15.0%) were synthesized by heterogeneous precipitation processing. The solid state reaction and nitridation reaction were completed at 1400–1500 °C for 12 h in a flow of N2–H2 (H2, 5 vol%). The phase of α-SiAlON was prepared at 1450 °C for 12 h. The phosphors showed strong and broad absorption in the range of 230–530 nm and a broad orange–yellow emission band ranging from 500 to 700 nm for peaking at 582–600 nm which were corresponding to the phosphor prepared by the conventional solid state reaction. The results indicate a concentration quenching effect at x≥7.5% and a systematic red-shift in emission wavelength as the heat-treatment temperature or the Eu2+ concentration increases. The quantum efficiency of the sample heat-treated at 1600 °C for 12 h, reached 70.56% (internal) and 45.7% (external) with the 450 nm excitation. The corresponding CCT (Correlated color temperature) range of white LED lamps consisting of a blue LED chip and the Ca-α-SiAlON phosphor can be ranging from 2000 to 2700 K.