Synthesis and photoluminescent properties of Eu3+-doped (1 − x)CaO-xLi2O-WO3 phosphors

A series of Eu3+-activated (1 − x)CaO-xLi2O-WO3 phosphors have been synthesized by solid-state reaction method. The X-ray diffraction patterns of the powder samples indicate that the CaWO4:Eu3+ is of tetragonal structure. The introduction of a small amount of Li+ ions (x < 10 mol%) have not led to its structure transition. However, when the Li+ content is more than 10 mol%, the X-ray diffraction patterns show that cubic Li2WO4 and rhombohedral Li2WO4 apart from tetragonal CaWO4 appear in the samples. The photoluminescent properties of the samples have been further studied at various Li+ content. The predominant emission locates at 616 nm for all the samples, corresponding to the 5D0 → 7F2 transition. It is found that the excitation intensities and thus the emission intensities firstly increases and then decreases with x increasing. The strongest emission at 616 nm appears at x = 0.5. Additionally, the excitation spectra reveal that the samples can strongly absorb ultraviolet (395 nm) and visible blue light (465 nm) and then transform the excitation energy to the red radiation. The excitation wavelengths at 395 and 465 nm are fitting-in with the widely applied output wavelengths of ultraviolet or blue LED chips. It means that the Eu3+-doped CaO-Li2O-WO3 material might be a feasible candidate for solid-state lighting applications.