[Preparation and luminescence characteristics of white-light emitting Ca9.95-xNa0.75K0.25(PO4)7: Eu0.05(2+), Mn(x)2+ phosphors].

ABSTRACT

The Ca9.95-x Na0.75 K0.25 (PO4)7 Eu.0.05(2+), Mn(x)2+ (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 and 0.7) phosphors were synthesized by high temperature solid-state reaction, and their phase composition and fluorescence emission properties were studied. Due to the existence of double phases with similar crystal structure, the 5d-4f transition of Eu2+ ions in the phosphors emits a fluorescence of wide wavelength with peaks located at 491 nm and 540 nm respectively. The energy transfer between Eu2+ and Mn2+, together with the occupation of Mn2+ ions at the eight coordination sites in the phosphors, makes the 4T1 (4G)-6A1 (6S) transition of Mn2+ ions eimit red emission peaked at 635 nm. The combination of fluorescence emtted by Mn2+ and Eu2+ ions results in the emission of white light with color coordinates (0.3335, 0.2924), (0.3999, 0.3179) and (0.3307, 0.2564). The nearly pure white light emitting makes the phosphors show great application potential in the white light-emitting LEDs.