Emission color shift from green yellow to reddish orange in Eu2+-activated Ca6BaP4O17 by doping high amount of activator ion

The most common white-light emitting diodes (wLEDs), which consist of a blue LED (InGaN) and a yellow-emitting Y3Al5O12:Ce3+ (YAG:Ce3+) phosphor, exhibit cool-white light due to the weak red emission of the phosphor. Thus, development of red-emissive phosphors that can be excited by blue light irradiation is critically important to improve the color reproducibility of the current wLEDs. In this study, we successfully obtained color-tunable Ca6(1-x)Eu6xBaP4O17 (x = 0.01–0.20) phosphors via the conventional solid state reaction. The emission color of Eu2+-activated Ca6BaP4O17 phosphors can be varied from green yellow to reddish orange by adjusting the amount of Eu2+ ions in the host lattice. As determined by Rietveld refinement, Eu2+ ions preferentially occupy two different crystallographic calcium sites, CaO7 and CaO8. Prototype wLEDs were fabricated and the optical properties of Eu2+-activated Ca6BaP4O17 phosphors, including photoluminescence, were systematically evaluated. Other properties such as lifetime and thermal stability were also studied. [Display omitted] •Color-tunable Ca6BaP4O17:Eu2+ can be obtained.•Emission color can be varied from green-yellow to reddish orange.•Eu2+ ion are located on two different calcium sites.