A new green phosphor, Ce3+-activated CaSc2O4, was developed, which shows green luminescence with a peak wavelength of 515 nm under excitation with blue light. Ce3+-activated CaSc2O4 can be used as a material for color conversion of white-light-emitting diodes (LEDs), which consist of a blue LED, a green phosphor, and a red phosphor, because the luminescence efficiency of this phosphor is comparable to those of commercial phosphors such as Y3Al5O12:Ce3+. The host crystal of this phosphor has an orthorhombic CaFe2O4 structure, and the Ce ion probably exists in an eight-coordinated Ca position. We investigated the dependency of the firing temperature and dopant concentration for luminescence intensity and found that the optimum temperature and concentration were 1600 degrees C and 1 mol % of Ce substituted to the Ca position. The luminescence peak wavelength was shifted toward longer wavelengths by replacing Ca with Mg. In contrast, replacing Ca with Sr resulted in a shift toward shorter wavelengths. (c) 2007 The Electrochemical Society.