We developed a new red phosphor, CaAlSiN3: Eu2+, which has a broad excitation band extended from UV region to 590 nm. At the optimum Eu concentration of 1.6 mol %, quantum output is seven times higher than for a conventional red phosphor, La2O2S: Eu3+, under 405 nm excitation. The phosphor is also more efficient than CaSiN2: Eu2+ or Ca2Si5N8: Eu2+ at any excitation wavelength. One reason of the high room-temperature efficiency is small thermal quenching, which is probably related to a rigid network of [SiN4] and [AlN4] tetrahedra. The phosphor is chemically stable as well. Accordingly, it is a promising material for warm-white light-emitting diodes. (c) 2006 The Electrochemical Society.