Near infrared quantum cutting of Na+ and Eu2+-Yb3+ couple activated SrF2 crystal

Na+ and Eu2+-Yb3+ couple activated SrF2 phosphor powders were synthesized by the co-precipitation method. The structure and luminescence properties of the system were investigated. X-ray diffraction data indicated that a mixture of cubic SrF2 and NaYbF4 phases gradually formed with an increase in the Yb3+ ion doping concentration. Diffuse reflectance has been used to confirm the existence of europium in the divalent state. The possibility of quantum cutting in the Eu2+-Yb3+ ions co-doped SrF2 crystal was discussed. Energy transfer that occurred subsequently from Eu2+ to Yb3+ was followed by an intense near-infrared (NIR) (∼1000 nm) emission spectral range. Emission spectra and the fluorescence decay measurements have been utilized to demonstrate the cooperative energy transfer in the Eu2+-Yb3+ couple ions. The energy transfer was completed at high concentration and the Yb3+ ions emission's intensity was reduced as a result of concentration quenching. In addition from the photoluminescence data it was also evident that Na+ induced a significant change to the NIR emission.