Vacuum ultraviolet spectroscopic properties of rare earth (RE=Ce,Tb,Eu,Tm,Sm)-doped hexagonal KCaGd(PO4)2 phosphate

Hexagonal KCaGd(PO4)(2):RE3+ (RE=Ce,Tb,Eu,Tm,Sm) were synthesized by coprecipitation method and their vacuum ultraviolet-ultraviolet (VUV-UV) spectroscopic properties were investigated. The bands at about 165 nm in the VUV excitation spectra are attributed to the host lattice absorptions. For Ce3+-doped samples, the bands at 207, 256, 275, and 320 nm are assigned to the 4f-5d transitions of Ce3+ in KCaGd(PO4)(2). For Tb3+-doped sample, the bands at 203 and 222 nm are related to the 4f-5d spin-allowed transitions. For Eu3+-doped sample, the O2--Eu3+ charge-transfer band (CTB) at 229 nm is observed, and the fine emission spectrum of Eu3+ indicates that Eu3+ ions prefer to occupy Gd3+ or Ca2+ sites in the host lattice. For Tm3+- and Sm3+-doped samples, the O2--Tm3+ and O2--Sm3+ CTBs are observed to be at 176 and 186 nm, respectively. From the standpoints of the absorption band, color purity, and luminescent intensity, Tb3+-doped KCaGd(PO4)(2) is a potential candidate for 172 nm excited green plasma display phosphors. (C) 2007 American Institute of Physics.