Discovery of new phosphors with desired properties is of great significance for developing high optical quality solid-state lighting. The single-particle-diagnosis approach is an effective way to search novel phosphors by analyzing tiny single crystals screened from the fired powder mixtures. In this work, a broadband orange-emitting phosphor of Sr3Si8O4N10:Eu2+ for solid state lighting was discovered by this method. The new oxonitridosilicate crystallizes in the monoclinic space group of P21/n (No. 14) with cell parameters of a = 4.8185 Å, b = 24.2303 Å, c = 10.5611 Å, β = 90.616°, and Z = 4. The crystal structure of Sr3Si8O4N10 was determined from the single-crystal X-ray diffraction (XRD) data of a single crystal, which is made up of a three-dimensional framework consisting of vertex-sharing SiN4 and SiN3O tetrahedra. Sr2+ ions occupy five crystallographic sites and have coordination numbers between 6 and 8 with one ordered Sr and other four disordered Sr atoms. The multiple Sr sites lead to a broadband emission centered at 565–600 nm and a bandwidth of 128–138 nm. The internal and external quantum efficiencies (IQE/EQE) of the title phosphor are 48.6% and 29.1% under 450 nm excitation, respectively. To improve the accuracy and speed of distinguishing phosphor particles in fired powder mixtures, a microscopic imaging spectroscopy is developed and demonstrated to modify the single-particle-diagnosis method.
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