White LEDs promise high energy-conversion efficiency, high brightness, low power consumption, long lifetime, small volume, and mercury-free, enabling them to replace traditional incandescent and fluorescent lamps for general lighting as well as traditional cold-cathodoluminescence fluorescent lamps (CCFL) for backlights of liquid crystal displays.White light can be generated by (ⅰ) combining individual red, green and blue LED chip (multi-chip LEDs); (ⅱ) pumping a yellow phosphor by a blue LED chip; and (ⅲ) combining red, green, and blue phosphors with an ultraviolet (UV) LED chip.In the latter two cases, which is also generally called phosphor-converted white LEDs, suitable phosphors with high conversion efficiency and useful emission colors are required.Traditional phosphors for CRTs or lamps cannot meet the requirements for white LEDs because of their quite low absorptions in the near UV-to-visible light range.This means novel phosphors for LEDs should be designed and developed.