Tunability of green-red up-conversion emission of co-doped Ca3WO6:Yb3+/Er3+ powders

Color tuning of Ca3WO6:Er3+/Yb3+ phosphors were prepared via high temperature solid method in this paper. The structure was investigated with X-ray diffraction (XRD) and the crystal morphology was observed through scanning electron microscopy (SEM). Visible up-conversion (UC) emissions were observed in green and red regions under the excitation of 980 nm diode laser. The luminescence study reveals strong S-4(3/2) to I-4(15/2) transition at 550 nm and strong F-4(9/2) to I-4(15/2) transition at 661 nm, respectively. In addition, it also can be observed that the green band is quenched and the red emission enhanced as the Yb3+ concentration increases. In consequence, the CIE coordinates changed from (0.30, 0.65) in the green region to (0.61, 0.38) in the red region at different Er3+/Yb3+ concentration. Thus, the tuning properties of Ca3WO6:Er3+/Yb3+ phosphors suggest that they could be good candidates for applications in lighting.