Mesoporous SrF2 and SrF2:Ln(3+) (Ln = Ce, Tb, Yb, Er) Hierarchical Microspheres: Hydrothermal Synthesis, Growing Mechanism, and Luminescent Properties

Uniform and well-dispersed SrF2 hierarchical microspheres have been successfully synthesized by a facile and friendly hydrothermal method. The experimental results indicate that such 3D hierarchical SrF2 microspheres with size about 1 mu m are assembled by numerous nanocrystals (about 100 nm). Nitrogen adsorption-desorption measurement suggests that mesopores exist in these hierarchical microarchitectures. The formation process of the hierarchical SrF2 microspheres and luminescence properties of SrF2:Ln(3+) (Ln = Ce, Tb, Yb, Er) microspheres have been investigated in detail. It is found that reaction time and trisodium citrate play a key role in forming the hierarchical microspheres. In addition, the lanthanide ions (Ln(3+))-doped SrF2 hierarchical microspheres show strong green (Ln(3+) = Ce3+, Tb3+) photoluminescence with 45% quantum efficiency and cathodoluminescence centered at 542 nm corresponding to the D-5(4) -> F-7(5) transition of Tb3+ under excitation of ultraviolet light and low-voltage electron beam, respectively. In addition, SrF2:Yb3+,Er3+ hierarchical microspheres show bright yellow upconversion emission under 980 nm laser diode excitation. The as-synthesized SrF2:Ln(3+) luminescent microspheres might find some potential applications in areas of photoluminescence and field emission displays