Radiation of light is available by radiation of heat or luminescence. The luminescence is emitted from mainly solid state materials called as phosphors when these are excited with several kind of energy. The phosphor consists of a host material and trace of ion(s) operating as luminescence center. The host materials must be pure and stoichiometric, and must not include impurities and defects to obtain strong emission. Many kind of phosphors have been developed for the progress of the field of displays and lighting.