Conversion of VUV to UV and visible in K5Li2LnF10 containing rare-earth from cerium group (Ln=La, Ce, Pr, Nd)

The potential of single crystals K₅Li₂LnF₁₀, for applications as VUV excited phosphors has been examined. The crystals were doped with lanthanide ions (Ce³⁺–Nd³⁺) with concentrations up to 100 at%. The self-quenching of luminescence is strongly reduced in this material. Luminescence spectra in the 50,000–10,000 cm⁻¹ range and excitation spectra in the 40,000–250,000 cm⁻¹ spectral range have been recorded at room and low temperature. Intense visible emission has been observed for Nd³⁺ and Pr³⁺. For the Pr³⁺ ions strong the ¹S₀–¹I₆ transition has been recorded only for concentrated crystals. Efficient conversion of VUV excitation to UV–VIS emission was observed in crystals doped with 3 and 100 at% of cerium. In both cerium-activated crystals the lifetimes of f–d transitions were equal to 32 ns.