Near UV-pumped yellow-emitting Eu2+-doped Na3K(Si1−xAlx)8O16±δ phosphor for white-emitting LEDs
A novel yellow-emitting phosphor, Na3K(Si1−xAlx)8O16±δ:Eu2+, peaking at 555 nm was synthesized and evaluated as a candidate for white-emitting LEDs. The structure refinement, luminescence properties of Na3K(Si1−xAlx)8O16±δ:Eu2+ phosphors as well as their thermal quenching and the fabrication of white-emitting LEDs were for the first time investigated. By partially substituting Si4+ with Al3+, the emission peak was shifted from 553 nm to 573 nm, giving a greenish yellow–yellow color, due to the splitting of the 5d energy level of Eu2+. By using a near-UV LED (395 nm) and a mixture of yellow-emitting Na3K(Si1−xAlx)8O16±δ:Eu2+ phosphor and blue-emitting BaMgAl10O17:Eu2+ phosphor as light converters, we constructed an intense white-light-emitting LED. The white-light-emitting LED exhibited an excellent color-rendering index Ra of 90 at a correlated color temperature of 5952 K with CIE coordinates of (0.33, 0.29). The results of the white-emitting LED package combining 395 nm near UV chip with Y/B phosphors demonstrated the potential of the yellow-emitting Na3K(Si1−xAlx)8O16±δ:Eu2+ phosphor for UV LED application.