Hydrothermal formation and up‐conversion luminescence of Er3+‐doped GdNbO4

The effect of concentration of Er³⁺ on the up‐conversion and photoluminescence properties of Gd_1.00?xEr_xNbO₄, 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?xEr_xNbO₄ solid solution was directly formed as nanocrystals by the substitutional incorporation of Er³⁺ into GdNbO₄ because of the gradual and linear decrease in the lattice parameters of the monoclinic phase corresponding to the Vegard's Law. The gadolinium niobate doped with 2 mol% Er³⁺, Gd_0.98Er_0.02NbO₄ 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% Er³⁺, Gd_0.80Er_0.20NbO₄ under excitation at 980 nm. These results demonstrate that the material, Er³⁺‐doped GdNbO₄ nanocrystals prepared through hydrothermal route and postheating has potential for up‐converting phosphor.