The highly efficient red phosphors (Ca1-xSrx)(S1-ySey):Eu2+,M3+ (M = Sc and Y) were prepared, starting from CaCO3, SrCO3, Eu2O3, Sc2O3, Y2O3, S, and SeO2 with a flux, by a conventional solid-state reaction. The optimized red phosphors converted 11.8% (Sc3+) and 11.7% (Y3+) of the absorbed blue light into luminescence. These quantum values are much higher than Q = 3.0% of CaS:Eu2+. For the fabrication of light-emitting diodes (LEDs), the prepared phosphors were coated with MgO from non-aqueous solution to overcome their weakness against moisture. White LEDs were fabricated by pasting the prepared red phosphors and the yellow YAG:Ce3+ phosphor on an InGaN blue chip (lambda(ems) = 446.5 nm). The incorporation of the red phosphor to the YAG:Ce3+ phosphor resulted in an improved color rendering index (Ra) from 70 to 80. (C) 2011 Elsevier B.V. All rights reserved.