Molten salt synthesis, characterization, and luminescence properties of GdNbO₄/LuTaO₄:Eu³⁺ phosphors

Graphical abstract: Well crystallized GdNbO4:Eu3⁺ and LuTaO₄:Eu3⁺ in the presence of fluxes were formed under reduced temperature in contrast to conventional method and their photophysical properties were studied. - Highlights: • Molten salt method was used to assemble two phosphors. • Both GdNbO₄:Eu³⁺ and LuTaO₄:Eu³⁺ could be red emissive. • The two powders were well dispersed as nano-particles. - Abstract: GdNbO₄:Eu³⁺ and LuTaO₄:Eu³⁺ have been successfully prepared with different fluxes (NaCl, KCl, NaCl and KCl) by the molten salt method. X-ray diffraction (XRD) patterns illustrated that well crystallized GdNbO₄:Eu³⁺ and LuTaO₄:Eu³⁺ in the presence of fluxes were formed under reduced temperature (900 °C) in contrast to conventional method (GdNbO₄:Eu³⁺: around 1200 °C; LuTaO₄:Eu³⁺: around 1500 °C). Scanning electron microscope (SEM) images revealed that well dispersed particles were achieved (granular or rod-like structures). Meanwhile, the photo-luminescent studies demonstrated that both niobate and tantalate are efficient hosts to sensitize europium red emissions. The results indicated that GdNbO₄:Eu³⁺ using NaCl as the flux gave much enhanced red emission whereas LuTaO₄:Eu³⁺ synthesized with the assistance of mixed salts (NaCl–KCl) achieved the best luminescence