A yellow-emitting Ca 3Si 2O 7: Eu 2+ phosphor for white LEDs

Abstract

A series of yellow-emitting phosphors based on a silicate host matrix, Ca 3 − x Si 2O 7: xEu 2+, was prepared by solid-state reaction method. The structure and photoluminescent properties of the phosphors were investigated. The XRD results show that the Eu 2+ substitution of Ca 2+ does not change the structure of Ca 3Si 2O 7 host and there is no impurity phase for x < 0.12. The SEM images display that phosphors aggregate obviously and the shape of the phosphor particle is irregular. The EDX results reveal that the phosphors consist of Ca, Si, O, Eu and the concentration of these elements is close to the stoichiometric composition. The Ca 3 − x Si 2O 7: xEu 2+ phosphors can be excited at a wavelength of 300–490 nm, which is suitable for the emission band of near ultraviolet or blue light-emitting-diode (LED) chips. The phosphors exhibit a broad emission region from 520 to 650 nm and the emission peak centered at 568 nm. In addition, the shape and the position of the emission peak are not influenced by the Eu 2+ concentration and excitation wavelength. The phosphor for x = 0.045 has the strongest excitation and emission intensity, and the Ca 3 − x Si 2O 7: xEu 2+ phosphors can be used as candidates for the white LEDs.