LaPO4: Tb, Ce phosphors have been used for the green component of three-band emission type fluorescent lamps.
We have confirmed that emission intensity of Tb3+ under 254nm excitation is greatly enhanced by the energy transfer from Ce to Tb in the case of the Ce co-doping, and the fluorescent intensity-temperature characteristics were also improved by substituting borate for a small part of phosphate, or by additive doping with thoriun.
In order to apply this phosphors to high pressure mercury lamps which operate at higher wall temperature and loading than low pressure mercury lamps, some characteristics of this phosphors under 365nm excitation were investigated. However, the green emission intensity under 365nm excitation was rather decreased by doping with cerium. The reason for this phenomena could possibly be caused to energy transfer from Tb3+ to Ce3+, as excitation spectra of Tb3+ and emission spectra of Ce3+ overlap each other.
Time-resolved spectra have been also observed under 365nm dye laser excitation. The 5D3→7Fj emissions were found in highly Tb-doped LaPO4: Tb, Ce phosphors, and new line emissions around 600nm were found in (La, Ce, Th) (PO4, BO3): Tb phosphors under 365nm pulse excitation which are considered to be originated to Ce2+.
