Deterioration of the performance of rare earth fluorescent lamps and phosphors after use, and these relationships were studied. In recent years, the demand of the recovery of valuable rare earth from used fluorescent lamps is increasing. However, recycling of rare earths is not progressing much because of the difficulty due to their chemical characteristics. On the other hand, recently, the reuse business of the materials recovered from used fluorescent lamps has begun in some places. Fluorescent lamps which are partially constructed from recycled materials are being slightly manufactured. Decrease in emission intensity of the phosphors was lower than that of fluorescent lamps. There are other factors such as consumption of mercury and emitter to reduce light quantity of the lamps. On the other hand, the main factor that decrease the emission intensity of the phosphors was concluded to contamination by adhesion of the emission materials made of lamp components, such as glass, mercury and emitter in this study. Although, chemical change, oxidation of the activator, and deterioration of the crystalline, those mean internal degradation of phosphor materials, were not significant. It is suggested that it becomes valid way to reuse the phosphors exhibiting a relatively high brightness, those are recovered from the fluorescent tubes cut off the portion surrounding the emitter, because the fouling by emitting substances is intense about that portion.
