Enhancement\nof Crystal Growth in Molten Salts by a\nCocrystallization Agent: Synthesis and Luminescent Properties of Ce<sup>3+</sup>- and Eu<sup>2+</sup>-Doped La<sub>3</sub>(SiS<sub>4</sub>)<sub&gt

In this study, we present the growth of large <i>Ln</i><sub>3</sub>(SiS<sub>4</sub>)<sub>2</sub>I (<i>Ln</i> =\nLa, Ce) crystals, both undoped and doped with Ce and Eu. The synthesis\nprocess involves the utilization of an arc-melted precursor in conjunction\nwith sulfur and KI. We investigate the role of Zr, Nb, Mo, and Ir\nas cocrystallization agents, facilitating the growth of relatively\nlarge (up to 6–7 mm) crystals. Our study suggests that Mo effectively\nacts as a cocrystallization agent for the synthesis of the Ln<sub>3</sub>(SiS<sub>4</sub>)<sub>2</sub>I and Ce- and Eu-doped La<sub>3</sub>(SiS<sub>4</sub>)<sub>2</sub>I phosphors. We confirmed the\nphase purity and crystal structure through powder XRD and single-crystal\nXRD analyses. The Ce- and Eu-doped compositions exhibit broad-spectrum\ntransitions from UV to visible regions. Photoluminescence spectroscopy\nanalysis reveals distinct emission bands for Ce-doped <i>La</i><sub>3</sub>(SiS<sub>4</sub>)<sub>2</sub>I at 430 and 490 nm within\nthe bluish region (0.15, 0.22 coordinates on the 1931 CIE chromaticity\ndiagram) upon excitation at 375 nm. Conversely, Eu-doped La<sub>3</sub>(SiS<sub>4</sub>)<sub>2</sub>I demonstrates an emission band at 578\nnm in the yellow-orange (0.45, 0.51) region following excitation at\n450 nm. Analysis of time-resolved spectra indicates multiple emissive\nbands contributing to the photoluminescence spectra. The average half-life\nof emission bands suggests fluorescence for (La<sub>1–<i>x</i></sub>Ce<sub><i>x</i></sub>)<sub>3</sub>(SiS<sub>4</sub>)<sub>2</sub>I and phosphorescence for (La<sub>1–<i>x</i></sub>Eu<sub><i>x</i></sub>)<sub>3</sub>(SiS<sub>4</sub>)<sub>2</sub>I phosphors.