Generation of tunable-emission in Li4Ca1-xSr0.96 + x(SiO4)2:0.04Eu2+ phosphors for LEDs application

A series of Li4Ca1-xSr0.96 (+) (x)( SiO4)(2): 0.04Eu(2+) (-0.4 <= x <= 0.6) phosphors were prepared by solid-state reaction method, and the photoluminescence properties were investigated in detail. By varying the relative contents of Ca2+ and Sr2+, the single-phase solid solution samples were obtained, which can be found from the corresponding XRD patterns. The excitation spectra of the as-prepared samples reveal that broad excitation bands appear and different excitation spectral shapes are observed by monitoring at 433 and 585 nm, which could be due to the various Eu2+ emission centers. Every emission spectrum includes two emission bands, and their relative intensities depend on the excitation wavelength and the Ca2+/Sr2+ concentration ratio. As a result, the tunableemission has been realized. The spectra characteristics for different Ca2+/Sr2+ concentration ratio in Li4Ca1-xSr0.96 + (x)(SiO4)(2): 0.04Eu(2+) further verify that two Eu2+ emission centers exist and the emission bands at 433 and 585 nm are attributed to the Eu2+ ions in Sr2+ and Ca2+ sites, respectively. The temperature-dependent photoluminescence spectra reveal that the Eu2+ emission centers in the Sr2+ and Ca2+ sites have different thermal stabilities, which results in the emission color changes somewhat for different temperature. (C) 2015 Optical Society of America