Morphology and photoluminescence properties of KSm(MoO₄) ₂ microcrystals by a molten salt method

Octahedron-like KSm(MoO₄)₂ microcrystals with monoclinic scheelite-type structure were successfully synthesized via a molten salt method using KCl as the reaction medium. The as-prepared products were characterized by X-ray powder diffractometer, scanning electron microscope, and photoluminescence spectrometer. The results show that the reaction parameters including calcining temperature, reaction time, and salt content play important roles on the morphologies and sizes of the final products. The possible growth process of the octahedron-like microcrystals was proposed based on the time-dependent shape evolution, which contained an oriented aggregation and Ostwald ripening process. Room temperature photoluminescence spectra of KSm(MoO₄)₂ microcrystals reveal the characteristic orange-red emission peaks at 565, 600 and 646 nm via ⁴G_5/2 → ⁶H_5/2, ⁴G_5/2 → ⁶H_7/2 and ⁴G_5/2 → ⁶H_9/2 electronic transitions of Sm³⁺ ions, respectively. These imply that the KSm(MoO₄)₂ microcrystals have potential application in the field of luminescence materials. The possible reasons for the difference in the relative intensities of photoluminescence are also discussed.