Preparation of Eu-doped CaGa2S4-CaS composite bicolor phosphor for white light emitting diode

A CaGa2S4-CaS composite doped with Eu2+' has been prepared by cooling the corresponding melt of the composition of 65CaS . 35Ga(2)S(3) containing 1 mol % EuS in order to obtain an efficient bicolor phosphor applicable to white light emitting diode. Efficient green and red fluorescence were simultaneously observed at around 555 and 645 nm, respectively, under 476 nm excitation. Especially, the red emission was about three times as intense as a simple mixture of CaGa2S4: Eu2+ and CaS: Eu2+ powders with the same composition. It was also found that the post heat-treatment doubled the red fluorescence. The obtained CaGa2S4-CaS composite doped with Eu2+ showed more intense fluorescence rich in color rendering than a commercially available Y3Al5O12: Ce phosphor.