Synthesis and Photoluminescence Properties of CaWO4: Eu3+ Phosphors

XD Red phosphors Ca1-1.5xWO4: Eu-x (3+) were synthesized with different concentrations of Eu (3+) ions by using a solid-state reaction method. The crystal structure of the red phosphors was found to be a tetragonal system. X-ray diffraction (XRD) results showed the (112) main diffraction peak centered at 2 theta = 28.71 degrees, and the size of crystalline particles exhibited an overall decreasing tendency according to the concentration of Eu3+ ions. The excitation spectra of all the phosphors were composed of a broad band centered at 275 nm in the range of 230-310 nm due to O2- -> W6+ and a narrow band having a peak at 307 nm caused by O2- -> Eu3+. Also, the excitation spectrum presents several strong lines in the range of 305-420 nm, which are assigned to the 4f-4f transitions of the Eu3+ ion. In the case of the emission spectrum, all the phosphor powders, irrespective of Eu3+ ion concentration, indicated an orange emission peak at 594 nm and a strong red emission spectrum centered at 615 nm, with two weak lines at 648 and 700 nm. The highest red emission intensity occurred at x = 0.10 mol of Eu3+ ion concentration with an asymmetry ratio of 12.5. Especially, the presence of Eu3+ in the Ca1-1.5xWO4: Eux (3+) shows very effective use of excitation energy in the range of 305-420 nm, and finally yields a strong emission of red light.