Rapid Production of Ln₂O₂S:Eu³⁺/Tb³⁺ (Ln = Sm, La, Gd, and Y) Phosphors by Molten Salt Electrolysis

Abstract

In this paper, a facile one-pot molten salt electrolysis method has been proposed for the synthesis of hexagonal sheet-like Ln 2 O 2 S:Eu 3+ /Tb 3+ (Ln = Sm, La, Gd and Y) phosphors. The phase, composition, morphology, and optical properties of the phosphors were characterized by X-ray powder diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and photoluminescence. The results showed that doping Eu 3+ or Tb 3+ causes no great changes to the crystal structure. Under the excitation of 394 nm light, sheet-like Ln 2 O 2 S:Eu 3+ (Ln = Sm, La, Gd, and Y) exhibited predominantly red emission at around 627 nm, which corresponds to the absorption of host crystals and the energy level transitions of 5 D 0 to 7 F 2 configuration of Eu 3+ ions. The sheet-like Ln 2 O 2 S:Tb 3+ exhibited characteristic excitation of Tb 3+ under 364 nm. The emission spectra of Ln 2 O 2 S:Tb 3+ (Ln = Sm, La, Gd, and Y) were measured, and those emission lines between 450 and 650 nm corresponded to the transitions of 5 D 4 to 7 F J (J = 0−6) ground state energy levels which belonged to the characteristic emission of Tb 3+ . The fabrication mechanism of the sheet-like Ln 2 O 2 S:Eu 3+ /Tb 3+ (Ln = Sm, La, Gd, and Y) was also investigated. This approach provides new avenues for the preparation of phosphors for applications in light-storing fields.

Ln10S14O (Ln = La, Pr, Nd, Sm) Oxysulfides: A Series of Direct n-Type Semiconductors

“…Initially misidentified as a lanthanoid sesquisulfide polymorph, β-Ln 2 S 3 , Ln 10 S 14 O represents a distinct tetragonal phase in which the oxygen atoms occupy the center of Ln (III) tetrahedra, surrounded by an intricate system of lanthanoid sulfide. 11 In comparison to the oxysulfides of formula Ln 2 O 2 S, which have been studied for their optical properties as phosphors, 12 imaging agents, 13 and sulfur-tolerant catalysts, 14,15 comparatively less information is known of their higher sulfur content congeners, Ln 10 S 14 O. 16−20 Having narrower band gaps as a result of the presence of quasistoichiometric sulfur, these oxysulfides have shown interesting photoluminescence 1616 and light absorption properties in catalytic systems.…”