The well-crystalline SrAlSi4N7∶Eu2+ phosphor could be synthesized by the solid-state reaction method using different types of Si3N4 raw material.The corresponding reaction mechanism was studied by means of X-ray diffraction (XRD),scanning electron microscopy (SEM),energy-dispersive spectrometry (EDS) and fluorescence spectra.It was found that the structural difference between α-Si3N4 and β-Si3N4,and the rearrangement of Si3N4 microstructures at high temperature had an important influence on the formation of SrAlSi4N7 phase.Results showed that the α-β transformation of Si3N4 was included in the synthesis reaction of SrAlSiaN7.So the reaction mechanism of SrAlSi4N7∶Eu2+ phosphor should be:α-Si3Na→β-Si3N4;β-Si3Na+AlN+Sr2N→SrAlSiaN7.The β-Si3N4 seeds addition were actually helpful to the grain growth of α-β transformation of Si3N4 and then increased the synthesis reaction rate of SrAlSi4N7.Pure SrAlSi4N7∶Eu2+ phosphor with higher luminous efficacy and better crystal morphology was finally obtained,indicating that the as-synthesized phosphor was an attractive candidate material as an orange-red component for warm white light LEDs.