Hydrothermal formation and up‐conversion luminescence of Er 3+ ‐doped GdNbO 4

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The effect of concentration of Er 3+ on the up‐conversion and photoluminescence properties of Gd 1.00− x Er x NbO 4 , x =0‐0.50 which has monoclinic fergusonite‐type structure as a main phase has been investigated, using a processing technique based on hydrothermal method. Under weakly basic hydrothermal condition at 240°C for 5 hours, a single phase of fergusonite‐type Gd 1.00− x Er x NbO 4 solid solution was directly formed as nanocrystals by the substitutional incorporation of Er 3+ into GdNbO 4 because of the gradual and linear decrease in the lattice parameters of the monoclinic phase corresponding to the V egard's Law. The gadolinium niobate doped with 2 mol% Er 3+ , Gd 0.98 Er 0.02 NbO 4 after heating at 1300°C for 1 hour, which has nanocrystalline structure whose crystallite size is around 29 nm, exhibits the highest photoluminescence intensity in the green spectral region, 515‐560 nm under excitation at wavelength of 254 nm. On the other hand, the up‐converted luminescence intensity of the niobate nanocrystals becomes the maximum at the concentration of 20 mol% Er 3+ , Gd 0.80 Er 0.20 NbO 4 under excitation at 980 nm. These results demonstrate that the material, Er 3+ ‐doped GdNbO 4 nanocrystals prepared through hydrothermal route and postheating has potential for up‐converting phosphor.