Influence of inorganic salt on morphology,particle size,and luminescence properties of lanthanide ions doped Na0.5Gd0.5MoO4 microcrystals

A variety of tetragonal Na_0.5Gd_0.5MoO₄ microcrystals with different morphologies, dimensions, side lengths, and heights (microplates, tetragonal, and quasi-cubic structures) have been synthesized by a novel inorganic salt assisted hydrothermal approach. The influence of the addition of inorganic salt NaNO₃ on the phase structure, morphology, particle size, and luminescence performance of the samples has been systematically studied for the first time. A series of Na_0.5Gd_0.5MoO₄:Ln³⁺ (Ln = Eu, Tb, Dy, Sm, Yb/Er, Yb/Tm, Yb/Ho) phosphors with excellent down-conversion or up-conversion luminescence properties have been synthesized by doping proper rare earth activator ions into the host matrix. The addition of inorganic salt NaNO₃ and the calcination process can greatly improve the luminescence performances of the phosphors, which can be ascribed to the decrease of surface area and enhanced crystallinity of the Na_0.5Gd_0.5MoO₄ crystals. The as-obtained down-conversion and up-conversion multicolor luminescent materials show the intense characteristic emissions of Ln³⁺ and eminent thermal stability. Moreover, the corresponding LED devices fabricated by the phosphors display dazzling multicolor emissions, which directly verifies that the as-synthesized phosphors may have the prospect to be utilized in the field of optoelectronic devices and LEDs.