One-step surfactant-free synthesis of KSc2F7 microcrystals: controllable phases, rich morphologies and multicolor down conversion luminescence properties

Homogeneous KSc2F7 microcrystals with controlled and abundant morphologies were prepared by a one-step hydrothermal route without employing any templates or surfactants. Particularly, uniform and well-defined KSc2F7 crystals with rod, sheet, flower-like, thin rectangular, xylitol-like and thin plate morphologies were achieved by manipulating the different environments of crystal growth, such as increasing the concentration of F−, changing pH and adding different surfactants. In addition, a phase transformation from monoclinic ScF3 to orthorhombic KSc2F7 was observed at different molar ratios of F/Sc and pH values, respectively. A more interesting thing is that the KSc2F7 crystals doped with 5% Ln3+ (Ln = La, Ce, Sm, Eu, Gd, Tb and Lu) showed rich morphologies and various sizes. The obtained KSc2F7:Ln3+ products showed multicolor emission with red (Eu3+), green (Tb3+) and blue (Ce3+), respectively. And the best emission conditions for KSc2F7 crystals are F/Sc/K = 3.5 : 1 : 3, pH = 7 and without any surfactants. The synthetic KSc2F7:Eu3+/Tb3+/Ce3+ phosphors may potentially be used for multicolor illumination and displays.