VUV–UV spectroscopic properties of RE (RE3+ = Ce, Eu and Tb)-doped KMLn(PO4)2 (M2+ = Ca, Sr; Ln3+ = Y, La, Lu)

The VUV excited luminescent properties of Ce3+, Eu3+ and Tb3+ in the matrices of KMLn(PO4)2 (M2+ = Ca, Sr; Ln3+ = Y, La, Lu) were investigated. The bands at about 155 nm in the VUV–UV excitation spectra are attributed to the host lattice absorption, which indicates that the optical band gap of KMLn(PO4)2 is about 8.0 eV. Ce3+-doped samples show typical Ce3+ emission in the range of 300–450 nm, and the energy transfer from host lattice to Ce3+ is efficient. For Eu3+-doped samples, the O2−–Eu3+ CTBs are observed to be at about 228 nm except KSrLu(PO4)2:Eu3+ (247 nm). As for Tb3+-doped samples, typical 4f → 5d absorption bands in the region of 175–250 nm were observed.