Broadband orange-emitting Sr <sub>3</sub>Si <sub>8</sub>O <sub>4</sub>N <sub>10</sub>:Eu <sup>2+</sup> phosphor discovered by a modified single-particle-diagnosis approach
Le Wang, Guozhen Ding, Shuxing Li, Shiro Funahashi, Takashi Takeda, Lu Yin, Pei Liang, Naoto Hirosaki, Rong‐Jun Xie
Abstract
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 Sr<sub>3</sub>Si<sub>8</sub>O<sub>4</sub>N<sub>10</sub>:Eu<sup>2+</sup> for solid state lighting was discovered by this method. The new oxonitridosilicate crystallizes in the monoclinic space group of <i>P</i>2<sub>1</sub>/<i>n</i> (No. 14) with cell parameters of <i>a</i> = 4.8185 Å, <i>b</i> = 24.2303 Å, <i>c</i> = 10.5611 Å, <i>β</i> = 90.616°, and <i>Z</i> = 4. The crystal structure of Sr<sub>3</sub>Si<sub>8</sub>O<sub>4</sub>N<sub>10</sub> 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 SiN<sub>4</sub> and SiN<sub>3</sub>O tetrahedra. Sr<sup>2+</sup> 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.