Red Fluorescence Enhancement via Using the Charge Compensation and Co-doping WO 3 in CaMoO 4 :Eu 3+ Phosphor for Ultraviolet Converted LEDs

Here we designed and synthesized the red Na x Ca 1−2x MoO 4 :Eu x 3+ phosphors with fluorescence enhancement via high temperature solid state reaction. Phase purity analysis, which had been checked by the X-ray powder diffraction (XRD), showed that all the obtained samples crystallized in a scheelite structure with the space group of I 4 1/a (No. 88). In these samples, we found that increasing the x value enabled shifting the XRD position to the low angle direction. For the photoluminescence (PL) properties, the charge transfer (CT) band as the x value increases exhibited an initial intensity increase followed by a subsequent decrease, and the optimal x value for the maximum CT band intensity was experimentally found to be 0.25. In sharp difference, directly exciting at the excitations of Eu 3+ , viz. 393 and 464 nm, allowed the Eu 3+ emission to constantly increase the emission intensity. In order to further enhance the red fluorescence intensity, the WO 3 was selected to co-dope into the Na x Ca 1−2x MoO 4 :Eu x 3+ (x = 0.5) sample in order to form the Na 0.50 (MoO 4 ) 1−y (WO 4 ) y :Eu 0.50 3+ solid solution compounds. Upon excitation at 393 and 464 nm, the y value that corresponded to optimal Eu 3+ fluorescence intensity was found to be 0.5. To illustrate our experimental observations, feasible mechanism profile was also given in this work. Our results have demonstrated that the Eu 3+ fluorescence in CaMoO 4 matrix could be enhanced by using the charge compensation and at the same time the WO 3 , which provided new insight into enhancing Eu 3+ doped crystals for ultraviolet converted white-LEDs.