Luminescent properties of (Y,Gd)BO3:Bi3+,RE3+ (RE=Eu, Tb) phosphor under VUV/UV excitation

Bi3+- and RE3+-co-doped (Y,Gd)BO3 phosphors were prepared and their luminescent properties under vacuum ultraviolet (VUV)/UV excitation were investigated. Strong red emission for (Y,Gd)BO3:Bi3+,Eu3+ and strong green emission for (Y,Gd)BO3:Bi3+,Tb3+ are observed under VUV excitation from 147 to 200 nm with a much broader excitation region than that of single Eu3+-doped or Tb3+-doped (Y,Gd)BO3 phosphor. Strong emissions are also observed under UV excitation around 265 nm where as nearly no luminescence is observed for single Eu3+-doped or Tb3+-doped (Y,Gd)BO3. The luminescence enhancement of Bi3+- and RE3+-co-doped (Y,Gd)BO3 phosphors is due to energy transfer from Bi3+ ion to Eu3+ or Tb3+ ion not only in the VUV region but also in the UV region. Besides, host sensitization competition between Bi3+ and Eu3+ or Tb3+ is also observed. The investigated phosphors may be preferable for devices with a VUV light 147-200 nm as an excitation source such as PDP or mercury-free fluorescent lamp.