La3+/Ce3+-codoped carbonitride phosphors-Y2Si4N6C were synthesized via a carbothermal reduction nitridation route. For the Ce3+-doped Y2Si4N6C phosphors, the emission spectrum exhibited a broad band at around 538 nm due to the f-d transition of Ce3+ ions. When La3+ ions were incorporated into the host, the emitting colors of (Y, La)(2)Si4N6C: Ce3+ phosphors varied from a yellowish green to blue region. The great blue shift in emission bands was due to the variation in the crystal-field strength around the activators. In addition, (Y, La)(2)Si4N6C:Ce3+ phosphors exhibited high thermal stability, indicating the superior suitability in ultraviolet light-emitting diodes.