Controllable hydrothermal synthesis of NaYbF4 and YbF3 with diverse morphologies and emission enhancement in β-NaYbF4: Er3+ upconversion micro-crystals via solvents codoping and Na+ dosage

As a matrix material, NaYbF 4 has attracted more and more attention due to its large absorption cross section and high energy transfer efficiency. In this study, lanthanide doped NaYbF 4 upconversion (UC) nano-/micro-crystalline was carefully synthesized by hydrothermal method . The influence of kinds of external conditions, including reaction time, initial reaction solution pH value, organic solvents codoping, and Na + concentration on crystalline phase, size, morphology and especially luminescent property are systematically studied and the possible formation mechanism based on PH values is emphatically proposed. The products of NaYbF 4 with various morphologies range from nanospheres , microprisms, microdisks, hexagonal crown-capped shapes, hexagonal clam-like shapes and hexagonal flower-like shapes were successfully prepared. The results show that the up-conversion luminescence property is positively correlated with the slenderness ratio. Solvents codoping and Na + concentration can greatly improve the luminescence property, especially for red emission. Impressively, the emission colors and intensities might be finely tuned through finely tuning the PH values, solvents co-doping and Na + dosage. Furthermore, this study will be expected to contribute to the synthesis of various morphologies and improving the UC intensity of lanthanide doped crystals.