Preparation of CaAlSiN3:Eu2+ red-emitting phosphor by a two-step method for solid-state lighting applications

In solid-state lighting applications, the CaAlSiN3:Eu2+ red-emitting phosphor can effectively improve the color quality of traditional white light produced by yellow phosphor conversion of light emitted by a blue chip. However, CaAlSiN3:Eu2+ phosphor synthesized by various methods usually consists of hard agglomerates with poorly dispersed particles, with consequently suboptimal luminescent properties. In this study, a two-step method is proposed in which a precipitation process is used to produce a precursor in the first step, and a high-temperature solid-state method is used to obtain the final product in the second step. NH4Cl flux is added in the second step to further improve the quality of phosphors. The main results show that: (1) CaAlSiN3:Eu2+ phosphor particles are well dispersed without any agglomerates, while the NH4Cl plays a key role in manipulating particle shape; (2) the photoluminescence intensity and external quantum efficiency of optimized CaAlSiN3:Eu2+ phosphor synthesized by the two-step method substantially outperform those of the corresponding commercial product.