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

A variety of tetragonal Na0.5Gd0.5MoO4 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 Na0.5Gd0.5MoO4: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 Na0.5Gd0.5MoO4 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.