Effect of NH4Cl additive on combustion synthesis of Eu-doped Ca-α-SiAlON phosphors

In this work, Eu-doped Ca-α-SiAlON phosphors were prepared by a facile and yet efficient combustion synthesis strategy with NH4Cl as an exclusive additive. The as-produced Ca-α-SiAlON:Eu2+ phosphors were featured with high purity, uniform crystal morphology of 3-5 μm in size and good luminescence properties with a yellow emission spectrum peaking at 578 nm under excitation of near-UV or blue light. Clearly, the intensity of emission spectrum for the product with 2 wt.% of NH4Cl increased remarkably, ∼50% higher than that of the absence of NH4Cl. The contradictory influences of the special additive NH4Cl on the photoluminescence behavior for the products were systematically investigated herein. With less than 2 wt.% of NH4Cl added, the effects of accelerating nitridation and crystallization dominated the combustion reaction. However, the effect of heat-absorption turned to be dominant when the content of NH4Cl was higher than 2 wt.%. With an increase in the content of NH4Cl, a continuous blue shift phenomenon in emission spectra could be observed and the concerning mechanism was uncovered.