Luminescence properties of nitrogen-rich Ca-SiAlON:Eu2+ phosphors prepared by freeze-drying assisted combustion synthesis

Nitrogen-rich Eu2+-doped Ca-α-SiAlON phosphors (Cam/2−xSi12−m−nAlm+nOnN16−n:xEu) were synthesized by a freeze-drying assisted combustion synthesis (CS) route. Fast-synthesized products with high purity and uniform particle morphology were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The analysis of lattice parameters by comparison with empirical equations showed that the as-prepared phosphors had low oxygen content. A series of samples were prepared according to the stoichiometry of Cam/2−0.08Si12−mAlmN16:0.08Eu for further research. The influences of m value on the luminescence properties were investigated in detail. As m increased, a redshift phenomenon was observed in both the excitation and emission spectra. First-principle electronic structure calculations showed that the 3d energy level of Ca played an important role in the occurrence of the redshift phenomenon.