RE2(MO4)3:Ln3+ (RE = Y, La, Gd, Lu; M = W, Mo; Ln = Eu, Sm, Dy) microcrystals: controlled synthesis, microstructure and tunable luminescence

RE2(MO4)(3):Ln(3+) (RE = Y, La, Gd, Lu; M = W, Mo; Ln = Eu, Sm, Dy) microcrystals with uniform shape and size were synthesized via a hydrothermal method using a polyvinylpyrrolidone (PVP)-assisted processes. The crystalline structure and morphology of these as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Possible reasons for the differences in crystal structures and morphologies were discussed. Furthermore, the photoluminescence (PL) properties of these as-obtained microcrystals were systematically investigated, which show strong and colorful emissions (white, yellow, red) under ultraviolet excitation. An investigation on the photoluminescence (PL) properties of La-2(WO4)(3):Eu3+ with different Eu3+ doping levels revealed the tunable emissions and the optimized Eu3+ doping concentration of La-2(WO4)(3):Eu3+.